In this next chapter I’d like to look at some childhood diseases that are particularly common in low-income countries and focus particularly on diarrhea and pneumonia, as they provide some very interesting examples of both how to prevent as well as how to treat these conditions so that the mortality and morbidity continues to go downward. The pie chart indicates the prevalence of each of these conditions in today’s world. You can see both diarrhea and respiratory diseases make up a large segment. And in some parts of the world, malaria is a major contributor as well. This is mostly in sub-Saharan Africa. Now here’s a child with a severe dehydration caused by diarrhea. Dehydration is the loss of fluid from the body. It’d be like if you took a grape and made it into a raisin or a plum into a prune. And you can see the child’s eyes are sunk back.His breathing would be deep and rapid. His pulse would be rapid. He’d have very little urine output. All signs of the loss of fluid and electrolytes. And here is a, a much younger child. And here you see the top of the head is depressed. This is called a fontanel, soft spot to many of us, before it closes. And here the dehydration has led to this sort of depression of the fontanel. Sometimes mothers would actually put mud or other substances there to try to draw this out, not recognizing that it might be due to dehydration. For a long time, in the summer months particularly through out the world, America, Europe and in lower-income countries you would see this scene in hospitals. Bed after bed after crib with children with diarrhea. And you could see here the dehydration, the loss of food and electrolytes are being replaced by I.V- intravenous solution. That’s fine if you have that solution, but in some parts of the world, this was very hard to come by. The IV solution wasn’t available or if it was available, it was expensive. You needed the tubing and the needle to insert and someone to do it. So there was a search for many years to find something that could be given orally, as this would eliminate the need or greatly obviate the need for interven…intravenous fluids. Now I show you this picture of a cholera cot, which is a wonderful piece of appropriate technology designed to be used with someone who significant diarrhea. And it’s simply a, a jute cot with a plastic sleeve that fits over it with a hole right where the buttocks would be. And that plastic sleeve goes into a bucket. So the liquid stool goes through the hole, through the sleeve, into the bucket. And one can then measure how much fluid has been lost. And the simple way of treating diarrhea is the patient gets exactly in what they have lost. And a way of measuring the level of hydration of course is whether they’re putting out urine and the concentration of that urine. Here’s a little girl who’s severely dehydrated. You can see again, that face that she looks. Again her pulse would be rapid. Urine output very low, rapid deep breathing. Now the mother is giving her an oral solution with the proper amount of electrolytes and glucose, that’s the magic ingredient. And to hydrate her. She’s alert enough to take it by mouth. And just a few hours later, here’s that little girl again and you can see a tremendous difference in the way she looks. The basic principle is simply this, a plant without water and you restore that plant by giving water and in the, in the case of diarrhea, electrolytes. Now what is the oral rehydration solution? It’s simply sodium chloride- table salt; sodium bicarbonate or Trisodium citrate; potassium chloride, and potassium is found in bananas and various fruits, citrus fruits; and glucose. Glucose is the key. And you can see on the other side that the sodium chloride, potassium bicarbonate and glucose are the millimoles per liter. In today’s solution, the sodium would be down to about 75 millimoles and the bicarbonate would be somewhat lower. And…. But that would be the major changes. Lower sodium chloride, slightly lower glucose and so on. But the basic principle and the basic composition remains the same. The message of course is to hydrate, hydrate, hydrate, because without the hydration other things can occur that will be a detriment to the individual, including circulatory collapse. To remind you, the…another side effect of continuous episodes of diarrhea is under-nutrition. Oftentimes because the mother will not necessarily feed the child, sometimes doctors recommend against it, unfortunately, and also the child may lose their appetite. Here’s a child who’s got severe marasmus. You can see the thin extremities. The child seems to be sensitive to light. The hair is thinning. And this is obviously a very poor family. Also the giving of a bottle of milk through the bottle can also be problematic if the water is not clean and if it sits out in the sun and bacteria are allowed to grow. Here’s a child who’s had multiple episodes of diarrhea and formula feeding. And you can see he has severe marasmus. So breastfeeding should always continue. And mothers should continue to feed their children if they have any appetite whatsoever, with whatever food is presently given to the child. So if the child wants to eat and the child is hungry, the child should be encouraged to eat. The teaching of this is best done of course in the community itself with three or four women who are taught now to prepare, shown how to prepare it and actually prepare it, which is what is being conducted here. You also notice lots of children around and these kids are picking up the message, just like their mothers are. And since children learn quicker than adults do, they’re going to carry the message into the community as well. One of the early tests of the oral rehydration therapy was in a refugee camp in 1971, refugee camps, where people from, refugees from what was then East Pakistan fled into West Bengal. And here they took up residence essentially in the pipes that were going to be placed in the ground to take away sewage. And when one lives in these kind of circumstances, you can guarantee that diarrhea is going to be a major problem unless there is strict attention paid to water and sanitation. And if that occurs then the treatment of this both in adults and children is essential. Another example of that is this is from a flood that occurred in Bangladesh. These occur periodically. This was 2007. And you can see individuals in an urban setting are trying to get clean water, even through a, a tube well pump which is almost totally submerged. This led to a major outbreak of diarrhea where up to 44,000 patients were seen at a treatment center within a nine-week period. What is interesting about this picture is that the family members are very much engaged in the treating of their loved ones. This is very critical because in these huge outbreaks it’s very difficult if not impossible for the medical staff to treat everyone. So one can engage family members who can be taught rather quickly how to deliver oral therapy and how to feed the patients and so on. And in that 44,000 cases, there was no one death from diarrhea and dehydration. This is a, an example of a packet that was found. This is for 500 cc’s which is now the standard in many countries. One liter is the standard in many other countries. So this, these salts can be given through a distribution scheme of these packets, as long as the packets are designed for whatever standard container people have. The next area I’d like to address is pneumonia, especially bacterial pneumonia, because this is what kills children. A number of years ago WHO developed what’s called an algorithm, a way of looking at pneumonia and deciding how to treat it given the severity. So in this particular algorithm you’ll notice on top that very severe pneumonia is defined as when the patient is confuse…cyanosis has set in. That is the child looks a bit blue, their lips look blue. They’re unable to drink. They’re unconsciousness, state of consciousness may be reduced. They’re clearly very, very sick. Severe pneumonia is when the lower chest in-drawing occurs and these children also need antibiotics. Where the respiratory rate is accelerated in the next box, going down, either above 50 is the child is two to eleven months or above 40 is one to four months, pneumonia is also the diagnosis. But if none of these occur, the child need not be treated for pneumonia. Now fortunately there are a number of vaccines that can prevent acute respiratory infection, many of which lead to pneumonia. Pertussis vaccine, diphtheria. Measles is a very important component, a very important vaccine. As is HiB conjugate vaccine, and the pneumococcal conjugate vaccine, two vaccines that have appeared on the scene in the last number of years that can make a significant impact on the incidence of disease. I put in meningitis because although it doesn’t cause pneumonia, it is a respiratory infection. Lastly I have this last picture in to remind us that malaria in some parts of the world can be a devastating disease to young children. This is simply an Aedes aegypti female, cause it’s only the female that takes a blood meal to help to grow her eggs. And you can tell the kind of mosquito by the white banding on the legs. So malaria can be a devastating disease to children, especially in low-income areas of sub-Saharan Africa. So what I’ve tried to do in the, in this chapter to point out that infectious diseases are certainly still with us and a major cause of morbidity and mortality, especially from diarrhea and pneumonia. But both of these conditions can be treated with oral solutions or I.V if necessary for diarrhea and antibiotics or other supportive measures for pneumonia. And both of them can be prevented through clean water and sanitation or vaccines, depending on the type of illness we’re talking about. The same by the way is true for malaria where the use of bed nets and early diagnosis can dramatically reduce the incidence of malaria, particularly in high incident countries.
Today’s chapter, is going to be on new and reemerging infectious diseases. Let’s again try to define these terms. Infectious diseases with an incidence in humans that have increased in the past thirty years or threaten to increase in the near future we tend to term new and reemerging infections. Now new infectious diseases that have come about in that, roughly in that time period would include HIV/AIDS, SARS, Lyme disease, Nipah virus, influenza H5N1 or H1N1. Infectious diseases are however often times emerge in new places and they are sometimes called reemerging diseases. This would be diseases such as West Nile virus and monkey pox. Then there are diseases that reemerge in drug resistant forms. A particularly worrisome group which includes malaria, multiple drug resistant tuberculosis, and some bacterial pneumonias and sexually transmitted diseases. Now there are a number of factors that have contributed to the arising of new and reemerging infectious diseases. These might include increased population density, inadequate infrastructures for water and sanitation, movements of people through travel and social disruption, the centralized production of food and it’s distribution, environmental changes, misuse and overuse of antibiotics and other drugs, changes in human behavior and sometimes dysfunctional governments. Let’s look at some of these in greater detail. In terms of the increase in population it was estimated that the population in 2000 was about 6.1 billion people and by 2050 this will come close…become close to doubling to 9.4 or 11.2 billion people. We’re also seeing a tremendous increase in urbanization going from 47% in 2000 to 60% to 65% increasing urbanization of the global population. Now as the population of the world increases of course there are going to be greater contacts between humans and wildlife in habitats that normally we don’t venture into and because of this interaction with both humans and our animals, we may see the rise of new viruses. The coverage of water supply, particularly in least developed countries, is also very problematic.
Particularly in both urban and rural areas in least developed countries the percentage that have access to potable water is anywhere from 50% to 60% Most of the drawing of water in rural areas and in urban areas is work of women. That is, they are the ones who are doing all the work of getting it from wells, from rivers and so on and taking that water back to their home. This is assuming that there is not an indoor water tap. And in this, the bringing of water into urban areas through trucks and so on where people are then forced to come to this area, collect the water, take it back to their home, is another way of distributing but it’s also very problematic as that source could be contaminated as well as the buckets and vessels which carry the water back to the home could also be contaminated. It also limits the amount of water that’s oftentimes available. The disposal of human waste is an increasing problem. The privies are directly linked to a body of water which connects to other parts of the city and that…that fecal disposal is of course quite unsatisfactory. We are increasingly discovering that open defecation may well be linked to under nutrition in children where this is a broad problem. The increase in travel both internationally and locally also provides opportunities for diseases to move about. We can move Ebola from one country into another in a matter of a few hours by air and we have seen this…this happen. No place in the world is unconnected to any other. We are really truly a global village. The production of food on an industrial basis has allowed for increasing availability of food, both grains and meat, but has also intensified the use of antibiotics and the raising of animals and where a central food supply is contaminated that contaminated food then travels far and wide. It’s not the same as getting milk from your local farmer or buying vegetables at the local farmers market. When we buy vegetables and fruits in many of our large cities of the world we have no idea where this comes from. Here’s the production of chickens in an industrialized production where thousands upon thousands of chickens are grown together in oftentimes extremely inhumane circumstances where they have no movement and so on and one can see that where a disease would enter this population it would destroy many, many chickens in a short period of time. This is of course quite different than what takes place oftentimes in local areas where there may be one purveyor of chickens from a few individuals in the community. Where ecology is involved is of course in climate changes, where temperatures have increased in certain areas which have allowed for the introduction of mosquitoes for example that had not been there in the past.
The tires are often traded internationally but when one trades in tires, there’s oftentimes water that is in the bottom of the tire and those…that water will you don’t need much to set up a breeding ground for mosquitoes. Those mosquitoes can then carry the viruses from where they came from to where they are going. And then the misuse of and overuse of antibiotics has led to the development of antibiotic resistance. We have only had antibiotics really for about 70 years. A blink in the eye in terms of evolution and yet we have managed to create a number of organisms that are extremely difficult to treat and far more expensive to treat. For example, multiple drug resistant tuberculosis is much more expensive to treat than is regular tuberculosis. Artemisinin which is the last, the latest drug we have to treat malaria, the last in the line, resistance is developing to that even though we treat these…malaria now with three drugs to try to avoid resistance to artemisinin. Tetracycline for cholera, multiple drug resistant gonorrhea which is a problem and in our hospitals, multiple drug resistant staphylococci which can infect wounds and cause devastating diseases. I would now like to focus on one particular new disease that has taken the world by storm over the last 30 plus years and that’s HIV which leads to AIDS. One might ask, where did HIV come from? Now is it a….. It’s defined as a new disease. It most likely came from somewhere in sub-Saharan Africa. There is a, an infection in some of the great apes, simian immune deficiency virus. It might well have been that someone in the forest or in a market was skinning a, a chimpanzee or a related species and cut themselves with a knife that carried the blood of this animal and therefore infected themselves. And unfortunately this virus adapted itself to humans. It then spread from that person through sex most likely, but it could have been through other means to another person and so on, until there was a critical mass of individuals who were infected and then the epidemic gradually increased. And then of course spread globally over time. We don’t know the initial events but it would seem to be that this was a zoonosis where the organism adapted itself very effectively to human beings. The distribution of HIV even though it came upon the world within probably five or six years it had been introduced everywhere, you can see that the distribution is of quite variable with most cases occurring in sub-Saharan Africa and if one looks at the population to case ratio, it’s even higher in that part of the world. Which raises an interesting question: why though HIV appeared in the world in many parts of the world around the same time, why has the spread been heterogeneous, not only globally, but even with the epidemic in sub-Saharan Africa? And I’d like to explore those ideas for just a moment to look at why this might happen and what does it tell us about prevention of these conditions? Now the spread of HIV in sub-Saharan Africa between 1984 and 1999 was quite interesting because it in 1984 it was fairly evenly distributed. By 1999 this had become a disease much more in the very southern parts of Africa and eastern Africa and West Africa in some parts have remained somewhat unchanged, Senegal, Mauritania, Niger, and so on. The dark red represents the highest prevalence of HIV. Now there are certain risk factors, I’ll call these proximal determinants that are associated with HIV/AIDS, the getting of…the obtaining of this infection. Clearly transfusion with contaminated bloods or contaminated needles and syringes which is like a mini-transfusion. Unprotected sex with a single or particularly multiple partners can increase your risk substantially. Mother to child transmission through delivery and breast feeding and interestingly the non-circumcision of men in certain parts of the world. Let me look at that last issue. Male circumcision interestingly enough is probably one of the oldest forms of surgery going back to at least 2200, 2300 years before the common era, as seen in this hieroglyphic from ancient Egypt. The circumcision rates in different countries in sub-Saharan Africa you can see are quite different with the highest level of…of AIDS in those countries which have the lowest level of male circumcision. Now why…why should male circumcision protect one? Well, it turns out that the inner lining of the foreskin contains cells which have a particular avidity for the HIV virus as well as the human papillomavirus which is associated with cervical cancer. Also when one removes the foreskin, the skin underneath hardens a bit and is more impenetrable probably to the virus itself. So there are biological reasons for why this particular simple operation reduces risks. We should remember that the initiation or the institution of…of male circumcision which by the way has nothing to do with female circumcision, was related to tribal or religious identity. It was not initiated initially to as any type of health measure. Certainly we didn’t know about these issues hundreds of years ago when these practices were introduced. Now distal determinants, that is those factors that affect the proximal determinants would be socioeconomic conditions, domestic violence, the status of women, the degree and type of migrant labor, sexual practices and values as defined by culture, and we have to be very careful that we don’t associate practices and values with any kind of ethical or moral character of the individuals involved. They have their antecedents in other…in other issues. And then concurrent partnerships. This is having many partners over a week as they have…having those many partners serially over the course of a year. Now what strategies then can we use based on these risk factors to reduce the possible risk for HIV? Well, if we delay the age of sexual debut that is when adolescents begin to have sex, we clearly reduce the time when they’re going to be exposed as we would be reducing the number and the exposure to high risk partners. If we reduce the degree of concurrency that would also reduce risk. If we limit alcohol and drug use prior to sex we make sure that the inhibitions to using condoms for example are not taken away. We can increase the level of male circumcision where the rates of HIV are very high and this would be again very much in southern Africa but not in…and East Africa but not in many other parts of the world. We could presumptively treat some sexually transmitted diseases to reduce transmission and certainly test the blood supply and needle exchange and syringes for I.V. drug users. One could also treat individuals who are HIV positive and thereby limit the transmission of this to their partners. This is problematic however and is not as easy to implement. If one looks at this schema of the HIV infection, one will notice that the first few weeks, months is when we have the highest level of viral particles in our blood, viremia. It is during that period of time when one is most likely to transmit the infection. So if one has a number of partners during that time, has sex shortly after one is infected, you are more likely to transmit the infection than when you enter the asymptomatic period which can go on for a number of years. Now we can measure the viral load in the blood and we can also look at other associated factors such as the CD4 count but it’s those first few weeks, months maybe, that we are most likely to transmit the infection because we don’t know we’re infected. There is no way of telling other than to do frequent HIV tests which is somewhat impractical. We can also reduce the risk of infection post exposure. That is, if someone is exposed, we can give nevirapine for the transmission, to reduce the transmission of mother to child. We can treat with ARVs as I noted post exposure or even give it prophylactically especially to high risk groups, people who have multiple partners for example. The use of vaginal microbicides has also been recommended but these are the factors that you can do post exposure. Clearly it’s far more practical if we can prevent the infection to begin with. Well, what I’ve tried to do in the…in this brief chapter is to look at new and reemerging infectious diseases. Why they occur, what are the risk factors in the modern day world. I then focused on HIV/AIDS as an example of a new and reemerging disease.
In this next chapter I want to take up the subject of zoonoses. Zoonoses is an infection or an infectious disease that is transmittable under normal and natural conditions from vertebrate animals to humans. It may be enzootic or endemic or epizootic or epidemic. There’s also another term, zooanthroponosis which is a disease transmitted from humans to animals. Now there are different types of transmissions with zoonoses. There is direct transmission, that is intimate contact with an infected animal, a person such as with a bite, a scratch, a spray by infectious urine, contact with fecal material, inhalation of a discharge, respiratory droplets due to coughing or sneezing, airborne spread, this is direct transmission. Then there is indirect transmission where there is an arthropod vector such as a flea, a mite, a mosquito, a tick and fomites such as cockroaches that are contaminated with the particular product going from an animal to a human. Another term we should be familiar with is species jumping. This is the transmission from animals to humans followed by human to human spread and this is the group that we are most interested in. That is, we shall see with HIV/AIDS, with SARS, with flu, that the particular agent went from an animal to a human and then began to spread from human to human. So the first one I’d like to take up is SARS or severe acute respiratory syndrome. If you’ll recall, this completely paralyzed the world a number of years ago because the mortality was quite high from this. Well, it turns out that SARS as we found out much later on was due to a particular virus called the coronavirus which was found in a particular animal called the civet cat which was slaughtered in some of the markets of…of China. But these civet cats had in fact been infected by bats, so it was bats that had the coronavirus, it infected the civet cat, the civet cat when they were killed, the spray of blood, sometimes people inhaled, they got it and they were then able to transmit it to other humans and it led to a type of pneumonia and if you’ll recall there were often pictures such as this from China, which is where the disease particularly had a major impact although it then spread to Honk Kong and Singapore and Canada and to Vietnam and so on. It never became the global pandemic that some of these conditions can become.
This is the latest of pandemics, this is the Ebola virus. Many of you have heard about this. It’s been particularly devastating in West Africa in this recent outbreak but it has occurred in central Africa as well, and let’s take a look at this particular virus which has been considered very contagious thought not very infectious. That is it can spread from one person to another through contaminated feces and blood and so on but doesn’t spread from person to person in a crowded room for example. It doesn’t spread through the aerosol route but rather through the blood and feces and so on of individuals who are infected and sick. They have to be sick with this disease. Here are some of these workers carrying…wearing these gowns to prevent them from having contact with this particular virus. This virus has probably, though we’re not sure, been spread by fruit bats, that is the bats again carry this particular virus. The bats may have contaminated food that was then eaten by an individual and that individual developed this disease, Ebola, and then spread it to other people through their bodily secretions. But it was the bat that originally harbored this virus, and then spread it, gave it to people and it was through the person to person spread that it has taken off. Let’s take a look at another one of these zoonoses. This is one called Nipah virus. Quite interestingly, again, this giant fruit bat and why they harbor these viruses we’re not sure and it’s very uncommon actually, would eat some of the fruit of these trees in Malaysia that were planted in areas where pigs were…pigs were grown. The pigs ate the fruit that fell to the ground and because this fruit was contaminated by the virus, the pig in eating the fruit developed an infection. When these pigs then were taken for slaughter and killed by, in the Abattoirs, the slaughterhouses, the men who were involved in this in the pig killing got the infection from the pig. So it went from a bat to the fruit to the pig to the people who were killing the pigs and up to 250 people about developed or died from this condition, a mortality of around 40% or 50% and this occurred in 1998 and 1999. And to get rid of this particular condition, first of all when the pigs became sick the first thing people did is they took them to market, so oftentimes these sick pigs, and they had developed a pneumonia, were taken to market and people would buy it unsuspecting that this might be this particular condition. And the way that Malaysia eventually got rid of this Nipah virus is they took pigs and they killed them and there is no longer a pig industry in Malaysia where at one time it was quite flourishing. This now takes us up to Bangladesh and in Bangladesh there was also an outbreak of Nipah virus and they couldn’t figure out how did this virus get into the human population. Because there were no pigs in that part of Bangladesh. It was a predominantly Muslim society and pork was not eaten, but they pieced together a story that showed that when these bats went to this date palm juice…now here’s a pot on a palm tree that is collecting date palm juice which is a sort of sweet juice that can also be made into something called gur which is a type of sugar. And when they would lick this because they’re fruit bats and it was very sweet and sometimes they would defecate into the pots. The men who sold this and this date palm juice was considered quite a delicacy would take it from house to house and sometimes this date palm juice was contaminated and individuals who took it would get Nipah infection and the mortality again was around 40% or 50%, sometimes 60%. This was a meningoencephalitis, that is it affected primarily the brain. Here are some bats flying just at dusk and they’re quite large, they have a large wingspan but they only drink fruit and sweet things. So the way to get rid of this was to put a skirt of bamboo over where the…the sap came from the tree into the pot and by doing this you can actually reduce the contamination of the date palm juice because the bat can not have access to that…to that sap that’s coming from the tree. So again a bat to the fruit, contaminating that, humans ingest it and it can spread from one person to another on…only on very, very intimate contact. And this is only through respiratory droplets, so it’s not like someone can walk into a room and cough and others would get it. You have to be extremely close to the individual to get this particular infection. So how do we control the transmission or the introduction of zoonoses? Well, this diagram here shows the linkage between wild EID is emerging infectious diseases, domestic animals and humans. And you can see that they interact. Now I’m not going to go through this entire graph but let’s just take a look at a few of the linkages. The linkage, say between wildlife and domestic animals. Here if domestic animals are closely associated with certain wildlife as we saw with the Nipah virus in Malaysia, there’s a spillover effect and these domestic animals can pick up the infection. If we look then down to the bottom of domestic animals and look at the food processing technology industry, we see that this virus got into humans through the infection in pigs which was then picked up in the slaughterhouses and then in humans it spread from person to person. So we have to break…break a number of these links between wildlife and domestic animals, between domestic animals and humans and even between humans and wildlife and so a lot of the strategies that have been developed to control zoonoses have focused on this type of diagram that we see here. All or most of the new and reemerging diseases, not all, will in fact be related to zoonoses so zoonoses are clearly very, very important and extremely costly. Bovine spongiform encephalitis or mad cow disease costs the U.K. over $9 billion in lost revenue. The Nipah virus which I just talked of cost Malaysia $540 million because of all the slaughter of pigs that had to take place. SARS which we started with cost China upwards of $50 billion because of the lost revenue from trade and tourism and so on and avian flu, H5N1 which we have not covered is going to cost billions and billions of dollars. In fact, another type of flu, H1N1 or what was called unfortunately swine flu, this is just a picture of the economic impact it had in Mexico where this beach would be filled with tourists at a particular time of year and of course it’s empty now because people are afraid and go elsewhere. What I’ve tried to do in this brief time is to talk about the importance of zoonoses. That is the diseases which linked animals to man and how they can spread, how they develop, SARS, Nipah virus are but two examples and there are many, many others. And then how they might be controlled and the economic impact that they can cause. We must be prepared to put much more attention into zoonoses and there is a global program called One Health which is trying to do just that.
In this chapter I’d like to look at the control, elimination, eradication and extinction of infectious diseases. Again, let’s look at some definitions here. By control we mean the reduction of the prevalence, that is the number of cases at any one time, incidents, the number of new cases over a period of time, to locally acceptable levels which is usually interpreted to indicate no longer a public health priority. Intervention however is still required. Elimination is the reduction of disease to zero and or infection to zero. The intervention, however, may still be required. An eradication is the permanent reduction of global, we’re now talking about the whole world, incidence of disease to zero with the organism not present in nature. No intervention at this point is required. And now let’s take a look at some of these terms as they play themselves out. The criteria for eradication which is the area I’m going to focus on in a moment is that humans are the only reservoir and there are no non-human vectors. Now we’re talking about eradication in people.The absence of a carrier state. That means that people don’t carry the organism even though they’re not sick. The feasibility of the intervention, is it effective? Is it acceptable? Is it affordable? Do we have ways to monitor whether this infection is present in the community, surveillance? Are people concerned and fearful enough that they will buy into these programs and does government have a strong enough commitment to try to eradicate a condition? Now infectious diseases that have been eradicated, there is only one and that is smallpox. And this was done primarily through a vaccine. Other infections that have been pretty much eliminated from many countries are guinea worm, which is only now found in some parts of sub-Saharan Africa, neonatal tetanus or the tetanus of the newborn. Again, vaccines here. There are still some cases but not very many even though the tetanus bacilli exists in the ground around us. Polio, we’re very close to eradicating this through vaccine but there are still cases in some parts of Africa and South Asia. Diphtheria, these have come way down, as has leprosy. The…but again, smallpox is the only human disease that we have been able to eradicate. There is a disease in cattle called rinderpest that has been eradicated, but this is the only one for humans. This is what smallpox looked like. It was a terrible disease. This child has lesions all over the body, it sometimes would in addition to causing a lot of deaths, it also caused blindness, and many other complications. This was a typical picture of a smallpox case. I’m now going to talk about the vaccine that was developed to deal with this. It was noted by Edward Jenner, a practitioner in rural England, that cow…that women who milked cows, cowgirls I guess you’d call them, did not get smallpox and he noted that on their hand was a lesion that was gotten from the cows that they worked with which was cowpox. He reckoned that if it protected these women and he took this from one woman who milked cows, Sarah Nelmes, that maybe this would protect people against smallpox. And in fact, he tried out the first vaccination was in 1796. Now prior to this, people had taken the serum, the lymph from the smallpox lesion of very mild cases and gave it to people hoping they would also develop mild disease. Sometimes it worked, sometimes it didn’t. Now despite the fact that this was shown to be extremely effective, there was a lot of resistance against this. This is a picture from a British publication, a humor publication called Punch and here is Jenner in the middle and people have cows growing out of their arms, their back sides, their face and so on. People figuring if they got the cowpox they might even turn into cows. Now, smallpox actually had eradication potential. What was that? Well, going back to those earlier criteria, there was universal fear, there was no animal reservoir, people were the only ones who had this disease. Nobody was a carrier, there was lifelong immunity after a single episode and a characteristic rash. There was no transmission from subclinical cases, as there were none. And we had a very, very effective heat stable ‘ (We didn’t need a refrigerator) vaccine and we had the development of a needle called the bifurcated needle which allowed us to easily transmit the vaccine to an individual. We also developed a very effective way of searching and containing this because smallpox moved relatively slowly through populations, once we found a case we could immunize around it so the case would be the orange circle there, we could then immunize around it, that would be the purple, and then we could also immunize the contacts of the contacts by taking these circles and moving out in this ring vaccination area we could reduce and eliminate smallpox from areas without having to immunize absolutely everybody in the population. We also minimize adverse events and we found that this vaccine was highly efficacious in preventing disease. The last case of…major case of variola minor occurred in Bangladesh in a young girl, Rahima Banu in 1976 and in 1977 the last case of variola minor appeared in Somalia in Ali Maow Maalin who just died recently. He devoted much of his life to also dealing with other disease elimination and eradication programs. The next disease I’d like to address is polio. Here are some children, we don’t see this very much anymore, because polio has almost been eradicated and has been eliminated from almost every country of the world. These children would develop paralysis, primarily in their legs, and in some places they would have to be beggars unless there was some way of looking after these children. In certain cases the disease affected the bulbar region of the brain and people would have to be on respirators, sometimes for lifetime because they could no longer breathe on their own. But with the polio eradication campaign globally we are down to now hundreds of cases rather than hundreds of thousands of cases. Getting those last few cases of course are extremely difficult so we can not say that this disease has been eradicated but it has been eliminated from probably 98% of the world. This is a very inexpensive, very efficacious vaccine. This is the oral vaccine. There’s also IPV which is an injectable vaccine but it is more expensive. If you look at the polio incidence by month, just in a four year period between 1994-98 in India, you can see that it was very high in 1994, peaked to over 110,000 cases, then came down in 1995 and at the end of ’95 and the beginning of ’96 they had national immunization days where they gave the vaccine to every child under a certain year. I think under five years of age. This was repeated again at the end of ’96 and ’97 and again at the end of ’97 and ’98 so that the number of cases came down dramatically. In fact, India has now been declared polio free and it has been eliminated officially from this country, which is a huge undertaking given the population of 1.2 billion There are other infectious diseases that have decreased dramatically in incidence, that is the number of new cases, with a significant reduction in mortality and morbidity. Measles is one of these which is a major killer, was a major killer of children. Rheumatic fever which affected the heart, hepatitis B which sometimes leads to liver cancer, and also peptic ulcer and helicobacter where treatment of these conditions with blockers of stomach acid and antibiotics has greatly reduced the incidence of these conditions. Here’s a child with neonatal tetanus, a condition which we rarely see today and that’s because now mothers are immunized against tetanus and they pass this immunity on to their child until that child can be immunized themselves. And lastly here’s a picture of measles which has been up until recently a major killer of children in low and middle income countries. So what I’ve tried to do in this last chapter is to review for you control, the terms control, elimination and eradication. I haven’t dealt with extinction because extinction means that there is no presence of this organism anywhere in the world and most of these organisms exist still in some laboratories. I’ve shown you eradication as it occurred with smallpox and the efforts that are going forward with polio. And lastly we’ve looked at a couple of diseases that have come down dramatically in their incidence and prevalence in the world.
In this lecture on infectious diseases, I’ll be covering a number of topics in the various chapters. This first one will be on the changing patterns of infectious diseases in time and place, that is looking at infectious diseases in a somewhat historical context.
I’ll also be covering the control or eradication and elimination of infectious diseases, zoonoses, emerging and reemerging infections, and lastly diarrhea and respiratory diseases in children as they are a major killer in this group of individuals.
Before we get into this historical look I want to give you some common definitions. What is an infectious disease? It’s a disease caused by the entrance into and growth and multiplication in the body of…of an individual of bacteria, Rickettsia, viruses, parasites, protozoans, fungi and prions. All of these are considered infectious agents. Another term which we should become familiar with is incidence. This is the number of new cases that occur per unit time. That time could be a day, a week, a month, a year. But time is very much a factor here. Prevalence on the other hand is the number of cases that occur at any one moment in time, today for example.
I’m going to give you an extremely abbreviated history of epidemics, that is a large number of cases occurring, although that number could be just one. And pandemics which are epidemics that cover the global world. Diseases associated with many of these epidemics include plague, smallpox, influenza, cholera, yello fever and measles. Now some of these are more historical because they don’t occur today, especially smallpox and plague and yellow fever, but they are important. An example of a devastating pandemic was the black death from plague that peaked in the 1346 to 1350 time period and it was estimated to have killed 30% to 70% of European population. Smallpox and tuberculosis, killed up to 90% of the indigenous population of the New World when they were introduced by the Europeans. Cholera pandemics began in 1816 and now take up, we’re in the seventh pandemic worldwide.
The largest single pandemic was that of the 1918 influenza pandemic which led to between 75 million plus deaths worldwide. These infectious diseases can be noted in history where they left their mark. For example in this mummy Ramesses V dated about 1157 BC we can see evidence of smallpox lesions. The pandemic epidemic that I want to focus on in the next pictures are those of plague. Plague was so common and was such a killer in Europe that there were dances of death that were developed to deal with the large numbers who were dying in various communities. This is a picture of a bubonic plague from one of the Bibles and we would probably not find these lesions to be consistent with plague today but this is the way people saw them. Doctors would oftentimes have very little to offer and would go around in these long black coats wearing these masks shaped like that of a bird’s head which limited the air that they would breathe in since they believed,in some cases correctly, that the miasma- the surrounding air, is what caused these diseases to occur in populations. People were so afraid and felt that the devil had entered their body and that’s why they would get these diseases that people would go around the countryside flagellating themselves to try to get rid of these evil forces and to show that they were deeply religious. Unfortunately, one of the things that often occurs in any epidemic or pandemic is we tend to blame the most impoverished, the poorest people who are there as we see them as the ones that have caused this to happen. And of course this is oftentimes very untrue. Jews who were burned alive because they were thought to be the cause of the Black Plague.
Oftentimes people were labeled as witches, as other non-desirables in populations and so that if we got rid of them, the plague would go away. Of course we even do this today and we’ve done it today with HIV/AIDS and other similar types of pandemics.
This is the organism that causes plague. This is called Yersinia pestis, it’s shaped a bit like a safety pin and these are transmitted through these fleas. Obviously not this large
but these fleas live on the body of rats, Rattus rattus and so oftentimes when there would be a rat die off these fleas would escape and then bite humans causing the plague. Sometimes there were large numbers of rats because the cats had been killed in some communities because they were seen as the animals of the devil. In addition to the tremendous number of deaths that occur, we also have to look at the historical changes brought about by any large pandemic. For example in the Black Death there were huge demographic changes. With 30% to 70% mortality in many areas of Europe, which took at least 150 to 250 years to recover. There were labor shortages, serfdom disappeared, wages became higher, labor saving technologies developed because there was a shortage of labor, land became plentiful, see these were all actually positive outcomes, despite the high numbers of death. However religious intolerance and the tradition of blaming others also increased and this was a time, oftentimes of religious intolerance that went through the countryside. Let’s go back to the terminology that we started talking about. If one is exposed to an agent, an infectious agent, a number of possibilities could occur. That is nothing, there could be clinical infection, the second line, or sub clinical infection or the person could carry the organism but not be sick. For clinical infection, one could see that death might occur, immunity that is what that an individual recovering from the disease might be immune or they might carry it or they might be non-immune and for the sub clinical infection of course there wouldn’t be death but immunity, carriage, and not-immunity might also occur. Also there are a number of factors that influence disease transmission and we should be aware of these. One is the agent itself which is the bacteria, viruses and so on. How infectious is it? What kind of illness does it cause?
What leads to its survival or death? Then there’s the host which is humans or animals, our age, our sex, our behavior, our nutritional status and so on, our health status, and then there’s the environment in which we live. What is the weather like? The housing? How crowded are people? What is the geography and what occupations do we have at the time that make it more susceptible. What’s the quality of the air, the food, our socioeconomic status and even the political nature of the situation. Now again, when something infects an individual there are a number of outcomes. An individual becomes infected and then there’s an incubation period which then leads to clinical disease or no disease. When somebody is incubating that infection, that is they’re not sick but that it’s growing in their body, there is a latent period. A period when they’re not infectious at all. They can become infectious, even before they get clinically ill, and it is during that infectious period that they can infect another. So you see in the first patient there’s the incubation and clinical disease, a latent period, in infectious period, and during that infectious period they infect the second patient.
This gives you an example of how infectious diseases have changed historically. In 1909 the percentages of infections in Chile causing mortality and morbidity was about 50%. Fast forward to 1999, those figures are now down to about 22%…23% so in 99 years, or in 90 years, we have seen a dramatic reduction in the importance of…of infections as causes of mortality and morbidity. We’re going to look at what we can do to reduce the importance of infectious diseases. There are a number of basis of infectious disease control. One, what is the quality of water and sanitation? What kind of water are we putting into our body? And how do we dispose of human waste and other waste? What about improved hygiene, hand washing for example. Housing- By decreasing crowding we can decrease diseases like tuberculosis. Improved nutrition also has a bearing because the host is stronger and able to combat certain infections. In the last 70 years or so we have developed incredible array of vaccines and antibiotics or antimicrobials. And lastly there have been certain behavioral changes. Here’s a young girl in a program that is teaching kids the importance of hand washing and how you can use soap and water to reduce risk, particularly after…after going to the bathroom for example. Unfortunately in crowded cities in many low income countries waste disposal through these latrines which are over-hanging a body of water in which kids sometimes swim and which are right across from a better off section of a city also leads to environmental contamination and increases the risk of the transmission of infectious agents. Far better that if we could put even this simplified form of a SanPlat latrine which people could use to get rid of waste rather than putting it directly into the water as shown earlier. Going back to vaccine development, the first one was in 1796 where Jenner used cowpox to in fact protect people against smallpox. We’ll see more of this later. In the 1800s we then had the development of rabies, cholera, typhoid and plague vaccine, but the huge increase occurred in the 1900s with diphtheria, pertussis, BCG which is for tuberculosis. In the 1950s we developed poliomyelitis vaccine and then in the 18…1980s, ’90s and to the present day there’s been a huge development in vaccines such as hepatitis A and B, pneumococcal rotavirus, meningitis, et cetera. The first antibiotics interestingly enough, this was not the first but one of the first, go back really to the late 1930s with sulfonamides but here is streptomycin, 1943 it was developed by Selman Waksman and first given to patients in 1944 for tuberculosis and you can see from this list of tuberculosis drugs that at least seven, and there are many more actually that have been developed since that first…since the first discovery of streptomycin. We now have other anti tuberculosis drugs which are used particularly against the drug resistant tuberculosis strains. Now lastly, I want to go back to our examination of the basis of infectious disease control and indicate a few other measures that we can use. One of these is surveillance and reporting, that is who is getting the disease, where are they getting it, and so on. So that we can then institute certain disease control programs, be it against malaria, other vectors, parasites. And we can institute preventive measures such as the promotion of hand washing, screening, education in schools, behavior modification, social marketing and so on and lastly the development of early and effective and affordable therapy to deal with the infections that are…have occurred in the past and will continue to occur into the future. So in this first brief lecture, I’ve tried to give you a few definitions of infectious diseases and how they might be transmitted. I’ve tried to look at the history of one of these, that is bubonic plague and pneumonic plague, and lastly to give you a brief outline of some of the basis for infectious disease control.
Doenças infecciosas em Crianças com foco nas diarreias e pneumonias
Neste artigo abordamos as doenças infecciosas nas crianças. Constituem um grupo mais vulnerável às diarreias e pneumonias, duas doenças com maior taxa de mortalidade e morbilidade. De seguida abordaremos as suas formas de tratamento, na diarreia através de soluções orais e soluções de intromissão, no caso das pneumonias, através de corticóides ou outras formas de tratamento Abordaremos as formas de prevenção, através das condições da sanidade, da vacinação. Por fim alguns tópicos sobre a malária, uma doença contagiosa com elevada incidência em África.
Diarreias e pneumonias
Nos países de baixo rendimento as doenças em crianças são bastantes comuns. As deficientes condições sanitárias e de abastecimento de água dão origem a frequentes diarreias e pneumonias. No gráfico abaixo pode-se observar a prevalência destas duas doenças no mundo actual. Ocupam a maior para do espaço, ainda quem em alguns lugares de África a malária seja predominante.
A diarreia provoca uma forte desidratação e a perda de líquidos pode conduzir à morte. Um criança em desidratação é também mais vulnerável a outras infecções. Os sintomas são fáceis de visualizar. Um estado de prostação, olhos ausentes, uma respiração rápida. É uma criança que não urina. Por vezes suam e as mães põem lama para secar, não se dando conta que isso ainda seca mais a pele.
Crianças em desidratação foram durante muitos anos um problema nos países quentes. Assim como no verão, a ocorrência de diarreias. O que é comum hoje nos países de baixa renda, foi comum no passado quando havia menos condições de saneamento. Também as crianças resistem de modo diferente dos adultos à falta de água e aos micróbios. O não beber água durante algum tempo pode ser normal para uma criança. A desidratação é normalmente tratada com soro. Uma solução intra-venosa que rapidamente recoloca os líquidos perdidos, seja por sede, seja por rejeição da água em caso de diarreia. Nos paíse mais pobres, no entanto essa é uma solução que nem sempre é viável. Ou não está disponível ou é cara, ou não existe pessoal preparado. É necessário entubar, colocar uma agulha na veia, e alguém que o saiba fazer.
Por essa razão é necessário saber que existem soluções orais que podem ser usadas. Por exemplo, num caso de cólera, é quase sempre necessário proceder à hidratação do paciente, o que muitas vezes só é viável através de soluções orais. Uma solução de cloreto de sódio ou bicarbonato de sódio, ou cloreto de potássio são boas administrações, que existem em saquetas preparadas. Alguna alimentos tem alguns minerais necessários que ajudam a fixar elementos. Por exemplo a banana tem potássio, que ajuda a fixar os líquidos. Por vezes é importante dar água com açúcar para aumentar a glucose. O importante nestes casos é hidratar para evitar o colapso do indivíduo.
Para saber, por exemplo, a quantidade de líquidos perdidos numa diarreia, é útil ter uma marquesa com um balde por baixo. A quantidade de líquido perdida é normalmente a quantidade de líquidos a repor no organismos. Uma das causas das diarreias frequentes é a má nutrição A desidratação dá prostração e alguma perda de apetite e a criança não come. Nem sempre os adultos vigiam a alimentação das crianças e não reparam que entram em marasmo.
A melhor forma de prevenir a necessidade de comer adequadamente e manter uma ingestão de líquidos adequados é através da educação na comunidade. A educação para a saúde ajuda todos a compreender os problemas e a desenvolver uma maior consciência sobre os diferentes sinais que podem indiciar problemas com diarreias e pneumonias. Há casos onde os problemas se colocam com um risco mais elevado. No caso deo campos de refugiados, onde as condições de vida nem sempre são adequadas, há que ter uma particular vigilância no domínio da alimentação e hidratação das crianças.
A pneumonia é outra das doenças que mais afetam as crianças. Causam problemas respiratórios graves e normalmente necessita de ser tratada com antibióticos. Apesar de haver várias vacinas que previnem diversos problemas respiratórios, é necessário perceber que várias doenças também dão origens a problemas respiratórios. A vacina para a tosse convulsa, para a difteria ou para o sarampo são tem alguns efeitos preventivos para prevenção de dos problemas respiratórios. Algumas vacinas anti-gripais que actualmente são desencolvidas constituem um instrumento eficaz nas infecções respiratórias.
Finalmente o caso da malária que em alguns sítios é particularmente severa com as crianças. Apenas a fêmea é infecciosa, quando retira sangue para alimentar. Os mosquitos podem ser identificados pelas sua parta com listas brancas. Nestes casos podem se tomadas medidas de prevenção, como evitar as horas de maior contágio (amanhecer e entardecer), usar roupas de protecção e dormir protegido. Usar repelentes e evitar concentrações de águas paradas.
Novas doenças infecciosas e reemergências
Neste artigo vamos abordar as questões sobre as mais recentes mudanças no campo das doenças infecciosas e como estão a acontecer essas mudanças. De seguida abordaremos o factores de risco no processo de globalização e finalmente aborda-se o caso do HIV/Sida, como exemplo das mutações que estão a acontecer no campo das doenças infecciosas.
As doenças infecciosas entre os seres humanos tem vindo a crescer nos últimos trinta anos, e a tendência é para aumentarem nos próximos anos, bem como surgiram mais tipos de doenças infeciosas e reemergiram velhas doenças com mais virulência. Há já novos tipos de doenças, como o HIV/SIDA o SARS (Síndroma Respiratório Agudo Grave) ou a Doença de Lyme (Lyme deseas), o virus Nypah ou a gripe H5N1 ou H1N1. Estas novas doenças aparecem por vezes em novos lugares e outras vezes ao mesmo tempo em vários sítios. Quando são doenças já conhecidas em outros lugares toma o nome de reemergentes, como é o caso do por vírus West Nile (Flavivírus) ou o Monkypox (o pox virus do macaco). Algumas das doenças que já são conhecidas, por sua vez, tornam-se resistentes aos tratamentos, caso da malária, a tuberculose multi resistente, algumas pneumonias bacterianas ou mesmo algumas doenças sexualmente transmissíveis.
Há alguns fatores que motivam estas mudanças. Aumento da população, aumento da taxa de urbanização e da sua densidade, infraestruturas de água e saneamento débeis ou em colapso, migrações e diversos problemas sociais, a produção industrial de alimentos e a concentração da sua comercialização, mudanças climáticas, mau uso dos antibióticos e dos medicamentos, mudanças culturais e mesmo alterações nas políticas públicas. São fenómenos que tendem a aumentar.
Fatores de risco
A população mundial , estimada no ano de 2000 em cerca de 6, 1 biliões, em cinquenta anos irá situar-se entre 9,4 e 11, 2 biliões. A taxa de urbanização era em 2000 de cerca de 47 &, deverá ser em cinquenta anos de 60 a 65%. há medida que a população aumentar irão também aumentar o contacto e a circulação de seres humanos. É também facilmente previsível que as condições ambientais se alterem com estes fluxos. Haverá certamente novos vírus a emergirem. São problemas que incidirão sobretudo nos países menos desenvolvidos aumentando os seus problemas. Por exemplo, nestes países, há ainda cerca de metade da população que vive em zonas rurais sem abastecimento de água e sem saneamento. A atividade de ir buscar água, nestas sociedade, é normalmente um papel desempenhado pelas mulheres. Isso aumentará o seu risco. Também o transporte de água das fontes para as cidades, muitas vezes feitas em sistemas pouco eficientes em termos de higiene é um risco que está a aumentar. Não será apenas a limitação dos recursos de água disponível, mas também os riscos da sua contaminação que poderão aumentar no futuros.
A disponibilidade de água é vital paras as comunidades humanas. Quer para o seu consumo, quer para as questões de saneamento. É cada vez mais claro que más condições de saneamento, nomeadamente a defecação em céu aberto está ligado à má nutrição de crianças que constitui um problemas adicional.
O aumento dos movimentos de pessoas é uma oportunidade para os vírus viajarem com mais facilidade. Por exemplo o Ébola pode passar dum país para outro em poucas horas, antes que qualquer sistema de alerta possa ser implementado. Todos os lugares do mundo estão hoje ligados em pouco tempo.
A questão da produção alimentar, com base na industrialização tem contribuído para um notável aumento das disponibilidades alimentares no mundo. Há mais cereais e carne. Mas esta produção também resulta do aumento do uso de antibióticos, que vão contaminando os alimentos e as diversas cadeias alimentares. Hoje é diferente consumir leite ou produtos da horticultura produzidos localmente do que consumi-los em espaços comerciais que os recebem não se sabe bem de onde nem em que condições foram produzidos. Todos conhecemos as condições de produção da frangos ou porcos em ambiente industrial. Uma doença que surge, e surgem com cada vez maior frequência, implica o abate de toda a produção. Se em alguns países esse abate é acompanhado pelos serviços públicos, em países com uma menor vigilância ou com um nível de corrupção mais elevado, as possibilidades de uma produção contaminada chegar ao mercado é maior.
As alterações climáticas também estão a afectar os habitats naturais. Por exemplo os mosquitos vivem em ambientes quentes e húmidos. O aquecimento global está a levar a uma ampliação dos habitats favoráveis para os mosquitos, que ampliam a incidência e ou a mutação das viroses
O uso indiscriminado de antibióticos, nos últimos 70 anos, está a produzir uma crescente resistência e a mutação do mundo biológico criando organismos resistentes.
O tratamento desta novas doenças é bastante mais caro. Por exemplo, a tuberculose multi-resistente tem um tratamento bastante mais dispendioso do que a tuberculoso comum. A artemisa, que era uma droga usada para tratar a malária, está a conhecer novas formas de resistência que dificultam o tratamento da doença. O mesmo da tetraciclina para tratar a cólera, a gonorreia multi resistente. E o resistente staphylococci que se transformou num problema nos hospitais de hoje e que está a infectar milhares de pessoas.
O Caso do HIV/SIDA
O caso do HIV/SIDA é um caso que ilustra bem o que está a suceder neste domínio das mutações das doenças infecciosas. O HIV é uma nova doença, que terá sido passada para humanos na África sub-sariana. Será uma doença endémica nas espécies dos grandes símios e terá passado por contágio para os seres humanos. É uma doenças que se transmite por contágios, do sangue ou da saliva. A pratica de atos sexuais potencia as possibilidades de transmissão. O que é surpreendente nestas doenças é que ela, tendo surgido nos anos oitenta, em cerca de uma década, rapidamente se expandiu, contagiando um elevado número de pessoas em todo o mundo. Sendo mais incidente nalgumas áreas (por exemplo na África oriental, onde se tornou epidémica), ela tornou-se uma infecção em todo o mundo.
É um caso de zoonose. Uma infecção que passa de um animal para o ser humano, tendo-se o microorganismos adaptado ao ser humano. A questão que interessa, para compreender este nosso problema das novas doenças infecciosas, é porque é que ele surge mais ou menos ao mesmo tempo em vários lugares do mundo, porque se espalhou tão rapidamente, não só globalmente, mas tão heterogeneamente, e que tipas de medidas de proteção podem ser tomadas.
Por exemplo, a sua expansão em África, tendo surgido por volta de 1984 e atingido o seu apogeu em 1999, a doença expandiu-se de forma muito intensa mas, olhando para a sua distribuição no mapa sub-sariano, mais numas regiões do que noutras.
É claro que o modo de infecção é feito pelo sangue, por transfusão ou por uso de seringas não esterilizadas. Por relações sexuais não protegidas. no caso das relações sexuais, a multivariedade de parceiros é um factor de crescimento da probabilidade de infecção. Pode passar pelo leite materno de mãe para filho.
Há na questão da prevenção uma interessante questão que se prende com a circuncisão masculina. A circuncisão masculina é uma prática antiga em África. todavia na África austral, onde a prática da circuncisão é menor, a incidência do HIV foi maior. Isso poderá esta relacionado com o modo de infecção, através da prática sexual. O indivíduo circuncisado, estará mais protegido pela células do prepúcio que produzem um pappilomavirus que evitam uma maior incidência do contágio.
Sendo um prática cultural, a circuncisão é antiga. Se contribui para evitar o contágio é importante conhece-la, mas não constitui uma prevenção eficaz. Muitas das doenças infecciosas tem uma maior incidência em situações em que os determinantes sociais são mais frágeis. As condições socioeconómicas, a violência doméstica, o estatuto da mulher, o tipo de trabalho, a condição de migrante, as práticas sexuais são todo um conjunto de condições culturais que influenciam o contágio e a disseminação das doenças infecciosas. em sáude pública é fundamental não envolver as questões dos valores e da ética das comunidades em que se trabalha ou com o caracter moral do paciente que padece duma determinada patologia.
A questão dos tratamentos dos doentes com HIV coloca este tipo de problemas. Sabemos que as relações sexuais e a troca de seringas aumentar a probabilidade de contágio. Para reduzir essa probabilidade era necessário que as relações passassem a ser protrgidas e a partilha de seringas evitada. Um processo que foi melhor implementado nuns locais do que noutros, através de programas caros, mas nem sempre é fácil de o fazer.
Por outro lado, no caso do HIV há também a questão do diagnóstico da doença. Dada a infecção, após as primeiras 3 semanas de elevada virulência de contágio e sem sintomas, o vírus hiberna por várias semanas ou anos para de seguida ir aumentando a sua capacidade de contágio. São factores que dificultam o rastreio da doença e a sua prevenção, pois durante o período de redução da virulência do vírus, a possibilidade de não ser diagnosticado em análise existe. Em teoria um indivíduo poderá estar durante um tempo bastante grande a ser portador e transmissor das doenças sem o saber e sem tomar medidas de protecção, dele e dos vários parceiros.
Como prevenção de contágio pós-exposição tem sido eficaz administrar nevirapina. Por exemplo para prevenir o contágio entre mãe e filho em processo de aleitamento. Há outros processo profilácticos podem ser administrados retrovirais, principalmente a grupos de risco. Um ato médico a ser seguido por profissionais.
Controle, eliminação e erradicação das doenças infecciosas
Controlar erradicar e eliminar doenças infecciosas são três conceitos que importa clarificar. Controlar, significa reduzir a prevalência e a incidência do número de casos da doença. Reduzir o número de casos novos num determinado período de tempo e reduzir a manifestação das doenças para um número considerado adequado para as condições de saúde pública do país. Para um nível que se considere que já não constitui uma prioridade para o sistema de saúde pública do país.
Eliminar uma doença infecciosa é reduzir a sua taxa de incidência ou da taxa de infecção para zero. Uma doença eliminada não significa contudo que não haja necessidade de manter um sistema de vigilância a um nível adequado. A doença pode não se manifestar, mas pode estar endémica e poder ocorres em função de variação de determinadas condições. A erradicação é a redução global da doença em todo o mundo. O agente já não está presente na natureza, e não é necessário qualquer intervenção.
O critério de erradicação implica portante que os humanos sejam os únicos reservatórios para o agente e não existam vectores de infecção fora dos humanos. Significa a ausência total de possibilidade de transmissão. Significa que não haja indivíduos portadores da doença, mesmo que não estejam doentes. Essa é uma situação que é rara. Apenas há um caso em que a doença foi globalmente erradicada: a varíola. Isso foi feito através da vacinação.
Há outras doenças infecciosas que estão próximo da erradicação. Por exemplo o verme da guiné, um verme que vive na pele de mamíferos em diversos países subsarianos e asiáticos ou o tétano neonatal, que também resulta de de vacinação. No nosso ambiente há já muito poucos bacilos do tétano, a poliomielite está muito próximo da erradicação, mas ainda se registam alguns casos em África e na Ásia. A difteria tem vindo decrescer, tal como a lepra. Mas estarem próximo da erradicação, significa que ainda existem. Em muitos locais estão eliminadas, significando que não existem riscos de infecção, mas que todavia podem surgir em função de movimentos de população.
A varíola é a única doença que foi erradicada porque já não há incidência nos animais, que eram os únicos portadores para os humanos. Nenhum humano transporta o agente e não há possibilidade de transmissão através de casos clínicos. Desenvolveu-se um sistema de vacina muito eficiente. Também foi feita uma investigação extensa e a doenças transmitia-se com muito pouca velocidade entre humanos. Apesar de no passado ter sido uma doença terrível, foi possível de identificar o agente e combate-lo. Os últimos casos de varíola registaram-se em 1976 no Bangladesh e em 1977 na Somália.
A próxima doença a ser erradicada poderá ser a poliomielite. Já há poucas incidências. É uma doença que desenvolve a paralisia dos membros inferiores. Por vezes desenvolve-se em regiões do cérbero e causa problemas respiratórios graves que conduz à incapacidade de respiração autónoma. É difícil de dizer que está erradicada, mas já foi eliminada em 98 % do mundo actual. Há uma vacina barata a eficiente para a poliomielite.
A poliomielite foi eficazmente combatida na Índia através da vacinação, nos anos noventa. Em 1994 havia um número elevado de casos. Através da vacinação de todas as crianças abaixo de uma determinada idade, em pouco mais de cinco anos registou-se uma redução substancial da incidência da doença, encontrando-se hoje praticamente erradicada.
Há outras doenças com decréscimo de incidências acentuado e que registam um número muito escasso de novos casos com uma diminuição acentuada da sua mortalidade. O Sarampo é uma delas, que foi uma das doenças mais mortais para crianças, sobretudo em paíse de baixo e média renda. A Febre reumática que afecta o coração, a hepatite B, que por vezes conduz ao cancro do fígado, a úlcera péptica ou o heliocobacter que com os tratamentos de antibióticos ou com vaso bloqueadores viram reduzir a incidência. O tétano neonatal é hoje raro de ver, porque as mães estão hoje imunes e não passam para os filhos.
Em suma se há apenas um doença erradicada, e eventualmente outra em vias de o ser, à uma grande conjunto de doenças que avançam para uma clara eliminação através das campanhas de vacinação e através de novos tratamentos.
As mudanças de padrões das doenças Infeciosas: Tempos e Lugares
As doenças infecciosas estão a mudar de padrão. É uma variação de padrão e de história. As mudanças derivam de medidas de controlo, de irradicação ou de eliminação das doenças infecciosas, zoonoses, doenças emergentes ou reemergentes, diarreias, doenças respiratórias nas crianças que criam ou podem contribuir para aumentar a mortalidade infantil.
O conceito de doença infecciosa é doenças que resultam da intervenção de um agente externo: o agente infeccioso. A Intervenção do agente infecciosos é um processo de entrada, crescimento e multiplicação, no corpo dum individuo ou indivíduos, de bactérias, vírus, parasitas, protozoários, fungos, Rickettsia e Prions.
Alguns termos são úteis para estudar ajudar a entender as doenças infecciosas: A incidência duma doença, é o número de uma dada unidade de tempo em que se manifesta a doenças, medida em números de dias, semanas, meses ou anos. A prevalência é o número de casos em que ocorre uma doenças num determinado tempo.
As doenças infecciosas manifestam-se ao longo da história da humanidade de diferentes formas. É útil entender a maneira como as epidemias se manifestaram, para compreender o impacto que tiveram na sociedade. Uma epidemia é um elevado número de casos de uma determinada doença que ocorre num determinado lugar. Um pandemia é uma epidemia que cobre todo o mundo, um fenómeno que é cada vez mais fácil de acontecer nos tempos atuais, devido ao elevado ritmo de trocas entre os diversos espaços geográficos. As principais doenças infecciosas são a cólera, a febre amarela, a peste negra, a gripe, a varíola, o sarampo.
As várias doenças tiveram diferentes incidências ao longo dos tempos. As doenças infecciosas também resultam de alterações na natureza que levam a diferentes formas de ocorrência. Por exemplo a Peste Negra, que afectou a Europa no século XIV levou a uma taxa de mortalidade que variava entre 30 %a 70 % em diferentes regiões. A varíola e a cólera, levada pelos conquistadores europeus para as Américas dizimaram praticamente 90 5 da população americana. O surto de pneumónica que eclodiu na Europa em 1918, provocou uma mortalidade de vários milhões de pessoas, que abalou um continente, já bastante fragilizado por causa das guerras. O efeito duma epidemia é bastante alargado com a globalização. Por exemplo, nos anos oitenta, a gripe asiática, foi um dos primeiros fenómenos que permitiu entender os riscos que as actuais sociedades enfrentas face a um surto ou mutação de um agente infeccioso.
No passado, o desconhecimento das razões das infecções levava a graves problemas sociais. Por exemplo, na Europa durante o século XIV acreditava-se que andar com bicos de pássaro, ajudava a prevenir a peste, o que de certo modo era verdadeiro, pois criava um espaço pouco favorável à inalação do agente infeccioso. Mas por vezes, acreditava-se que a doença era motivada por intenções malignas de alguns membros da sociedade ou por aqueles que praticavam ações fora do que se consideravam “normal” ou correcto. As crenças conduziram a grandes violências e mortandades na fogueiras ou a ostracismo de todo o tipo de minorias, com acusação de feitiçaria ou de serem hereges. A ignorância é pois um elemento que agrava os efeitos das epidemias. Nos dias de hoje, algumas doenças infecciosas, como por exemplo o HIV/SIDA também produziram, sem razão, ostracismo de grupos sociais que podem ter resultados negativos no controlo da doença.
Se alguém é exposto a um agente infeccioso, com elevada probabilidade pode suceder uma das seguintes situações:
Mesmo que não haja infecção, o agente pode transportar o agente infeccioso e transmitir a outro indivíduo. Por essa razão devem ser tomados procedimentos adequados a evitar a propagação da doença através da restrição e controlo de movimentos das população, o que nem sempre é eficaz.
Algumas das questões que afetam ou influenciam a transmissão do agente infeccioso passam por saber e registar as seguintes questões:
- Qual é o agente. Saber se é uma bactéria, um vírus ou outro agente;
- Como é que se apresenta (sintomas) da infecção;
- Qual a causa da doença e de que tipo de trata,
- Saber se o desenvolvimento da doença conduz à morte e qual a taxa de sobrevivência;
- Saber se há um hospedeiro animal que transmite ao humano, ou se á uma transmissão entre humanos,
- Saber, nos casos ocorridos, a idade, sexo, a profissão, o comportamento, o estado nutricional, e pode também ser útili recolher informação sobre o estatuto social;
- Saber qual o ambiente é que o doente vive (condições da habitação e sanidade)
- Qual é o clima predominante, em termos de temperatura e humidade relativa,
- Quais são as crenças predominantes e que tipo de procedimentos as crenças apontam para situações de doença
- A qualidade do ar, da alimentação das populações da área de incidência e qual a extensão dessa área.
Um dos principais problemas das infecções nos indivíduos, com implicações nos processos de controlo, relaciona-se com o processo em que a doença está em incubação, ainda sem sinais exteriores, mas que já pode ter tornado o indivíduo num agente infeccioso. É importante ir fazendo o rastreio das doenças para saber a sua possibilidade de extensão no grupo social ou área geográfica onde o indivíduo se moveu.
Mudanças nos padrões das infecções
Nos últimos 100 anos as doenças infecciosas tem vindo a ser reduzidas e controladas na maior parte dos países. Há uma nítida redução da mortalidade e da morbilidade produzida por doenças infecciosas na maior parte dos países. Algumas das razões para essa alteração tem a ver com as melhorias no abastecimento de água e saneamento, na capacidade de reduzir a incidência da tuberculose, uma melhor cultura na sociedade em relação os comportamentos básicos de higiene, sobretudo na educação das crianças. Regras como lavar as mãos ou tomar banho com frequência tem sido bastante eficientes. No entanto, não existem iguais condições em todos os lados e sítios urbanos. Os locais onde as latrinas são a ceu aberto ou ao ar livres, onde não há águas tratadas, ou onde o consumo de água é feito em locais de águas estagnadas, são exemplos de locais de elevado risco que implica tomar medidas de saúde pública. Por exemplo criar latrinas sem contaminação para o ambiente, ou evitar deitar dejectos para o exterior, ferver as águas para alimentação são medidas eficazes para diminuir os riscos.
Um outro processo de evitar as doenças infecciosas é a vacinação. Há muitas doenças infecciosas que são hoje muito menos incidentes do que no passado pela utilização de vacinas. A primeira vacina foi produzida em 1796 e foi usada contra a varicela. No século XIX surgiram as vacinas contra a Raiva, a cólera, a febre tifóide e a bubónica. No século XX contra a difeteria, a tuberculose, e tosse convulsa. Nos anos 50 contra a poliomielite, e nos anos oitentas, contra a hepatite, A e B, a meningite e contra vários pneumococos. A utilização das vacinas permitiu diminuir de forma acentuada a incidência das várias doenças. Contudo, nem todas as vacinas estão disponíveis em todos os lugares e a sua aplicação não ocorre ao mesmo tempo em toda a população.
Um outro fator que ajuda a combater as infecções produzidas pelas doenças infecciosas foi a descoberta dos antibióticos. Em 1930 os sulfamidas e em 1944 cura da tuberculose. A combinação da vacinação, como prevenção, e dos antibióticos, como terapêutica, levaram a uma forte recessão da incidência deste tipo de doenças, e à erradicação de algumas.
Há no entanto que manter algumas medidas para vigiar e controlar as doenças infecciosas. É necessário manter a vigilância e relatar as suas ocorrências. É necessário saber quem tem e como apanhou a doença. Há que manter com habtio as regras de higiene e sanidade. Lavar as mãos, a educação nas escolas, monitorar a evolução das doenças, observar os comportamentos sociais e manter o marketing social. É necessário estar vigilante e aplicar correctamente as terapêuticas. No campo das doenças infecciosas, o tempo é determinante par controlar o alargamento da incidência das doenças. As doenças infecciosas vão continuar a desenvolver-se no mundo e vão continuar a ocorrer. Uma boa redução das taxas de incidência e mortalidade não implica uma diminuição dos esforços de vigilância.