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Disease and the developing world
Entry 152 of 194 | show all | print this entry |
(Amy)
After three months of malaria prophylaxis, the kids let off a collective cheer the first morning they didn't have to take their "disgusting" meds. Every morning, however, I was acutely reminded of what a luxury they were, of the thousands of mothers that day who would watch the fever rise in their child and worry about whether that child would survive the coming days.
Malaria, which kills several million people each year and sickens countless others, is carried by the anopheles mosquito. Because these mosquitoes bite at night, the use of insecticide-treated bed nets significantly decreases the chance of being infected. There was a really interesting article in the February 2nd edition of The Economist magazine called Net Benefits. A huge survey by the WHO found that providing free (not lost-cost, which should be more effective according to the popular wisdom), bed nets cut the malaria death rate by at least half in the under-fives when distributed on a mass scale. It estimated that a five-year, $10 billion campaign that had three aims-providing insecticide-impregnated nets free to anyone visiting a clinic, giving away arteminisin-based drugs, and spraying the inside of people's houses with DDT, would reduce the death rate to thousands each year. That would be a huge improvement while we wait for an effective vaccine to be developed.
This kind of vulnerability made me wonder about other mosquito-borne diseases, ones that many of us have heard of but don't think about much, such as yellow fever, dengue fever, Japanese encephalitis, and West Nile. These diseases, which are mostly transmitted by the aedes aegypti, or striped house mosquito, currently kill fewer people than malaria but still have the potential to inflict great harm. For starters, aedes aegypti bite repeatedly during the day, so bed nets are not very effective. Since they are attracted to carbon dioxide and lactic acid, which are heavier than air and therefore settle closer to the ground, mosquitoes bite people most frequently on their feet and ankles. For people walking through tall grasses or children playing barefoot near pools of water, it is very difficult to prevent being bitten. Interestingly, the favorite urban habitat of these mosquitoes is inside discarded tires, which are thought to closely simulate the tree trunks deep in the African jungles where they originate.
Yellow fever is explored in wonderful depth and detail in a new book called The American Plague by Molly Caldwell Crosby. She writes much about Memphis, Tennessee, which was almost destroyed by the epidemic of 1878, but also mentions how the virus, which was brought over on slave ships, infected 500,000 Americans, killing 100,000 of them. We stopped routinely vaccinating against the disease years ago, and it is mentioned as a potential biological weapon. If a serious outbreak were to occur in the U.S., due either to travelers returning from areas where people are routinely infected (like Africa or South America) or from a bioterrorist attack, we could see hundreds of thousands of deaths before the epidemic was brought under control. Trends do point toward more deadly outbreaks affecting us in the future, so an awareness of how to minimize its impact is really important.
There are over 100 million cases of dengue fever every year. It is usually not life-threatening, but if it develops further into dengue hemorrhagic fever (characterized by bleeding) or dengue shock syndrome (where the patient goes into shock), the mortality rate rises to 3% if treated, 50 % if untreated. It is most prevalent in Southeast Asia, and we were very moved by all of the affected children we saw in Cambodia.
Japanese encephalitis is another disease endemic to southeast Asia, one that we hadn't thought much about until we needed the vaccinations for this trip. Domestic pigs and wild birds normally harbor the virus, and everybody's happy until a mosquito bites an infected animal and then bites a person, allowing the virus to pass during the feeding process. Then comes the fever and the headache, and mortality rates range from 0.3% to 60 %. Again, we could afford the vaccine (even though the kids begged to skip it and go directly to Dairy Queen); millions of people cannot.
West Nile is a virus that is probably familiar to many Americans. Since the first cases were reported in 1999 in the U.S., we've been told what to watch out for. Although it usually remains asymptomatic, some people will develop fever and flu-like symptoms and in some number of cases, the disease will develop into meningitis or encephalitis. In 2007 alone, of the 3623 West Nile cases reported in the U.S., 1213 of them involved brain inflammation, and 124 people died. As mosquitoes lay their eggs in pools of standing water, eliminating these sources is one of the most effective ways of controlling the mosquito population. It's also important to report dead birds, especially crows and blue jays, because they usually indicate the presence of the virus in an area before any human cases are seen.
Now, of course, bird flu (avian influenza) is the disease we hear the most about. Last week in China, the twelfth case of human-to-human transmission was reported. We've all heard about what could happen if the virus gained the ability to spread easily from person to person. In the West, many people could die, as identifying and developing a sufficient vaccine supply would take four to six months.
But getting back to vulnerability, it is still the developing world that would be hit the hardest. Developing countries have fewer stockpiles of expensive antiviral medications, which should help to stop the spread of the virus. It is more difficult to identify cases in counties with a poor public health infrastructure and, in turn, harder to quarantine infected people. Lower literacy rates in many (but not all) developing countries make education more difficult. When we were in India during the latest outbreak, we were told that people were hiding their diseased birds instead of reporting them because government compensation for the loss of their birds might not come for weeks, and they did not have a financial cushion that would allow them to wait that long.
The 150 or so viruses that reside in the animal population but either cause or have the potential to cause illness and death in humans are not something we think about much here. Many of these diseases reside in monkeys and apes, often in the jungles of Africa and southeast Asia. In terms of the diseases that are transmitted by mosquitoes, much of the world does not have the resources to control their mosquito populations. The U.S and Europe became wealthy enough to destroy many mosquito habitats, effectively eliminating diseases that killed huge numbers of people in the West. What is our responsibility toward those who simply were not fortunate enough to be born in a place where suffering and death from infectious diseases were not part of the daily routine?
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