Monday, May 30, 2011

How to Eradicate Malaria

On April 25, 2011, the United Nations observed World Malaria Day by setting an ambitious goal: zero malaria deaths by 2015. Few diseases have contributed more to the misery of mankind than malaria has. At its apex in the 19th century, malaria was responsible for over half of all deaths in some of the hardest hit nations like India, and was endemic to temperate and tropical zones alike. Over the last 150 years, dramatic progress has been made. Malaria has been completely vanquished in the United States and Europe, and sharply reduced in Latin America and South Asia. But Sub-Saharan Africa remains a problem, as it tragically does for many infectious diseases. Today, malaria still kills nearly a million people per year. It is responsible for 20% of all child fatalities in Africa, making it the second-biggest killer in Africa behind HIV/AIDS. Even these high figures probably underestimate malaria’s true consequences, because one of the symptoms of malaria is to weaken the immune system and increase the viral load of diseases such as HIV/AIDS. The disease also makes it difficult for nations to escape poverty; developmental economists John Gallup and Jeffrey Sachs estimate that economic growth is reduced by 1.3% per year in countries with widespread malaria.

Why has malaria remained so troublesome in Africa, even while declining elsewhere? Malaria has always been a disease of poverty. In impoverished countries, many makeshift homes do not have screens, doors, or windows to keep mosquitoes out. Additionally, poor people are often unable to afford malaria treatment, which can cost the equivalent of several months of income in some African nations. If it is left untreated, malaria does not simply run its course and disappear from the body like many diseases do. Instead, it goes into dormancy and can strike again months later. Malaria can become a chronic, lifelong problem for some of its victims who do not have access to treatment. In societies in which a large fraction of the population carries malaria (even if it is dormant), mosquitoes are more likely to acquire the disease each time they bite, and therefore more likely to transmit the affliction to new victims.

In spite of the depressing facts surrounding malaria, there is good reason to believe that malaria can be eradicated in the near future. The UN’s goal is probably overly ambitious, but perhaps only by a few years. A number of trends are converging to make it possible to eliminate the disease. The use of mosquito bed nets has become much more common in many African nations. In Rwanda, 56% of young children now sleep under a bed net, compared to just 4% a decade ago. In Kenya, 46% do so, up from just 3% a decade ago. The mosquitoes which carry malaria tend to be nocturnal and prefer to bite indoors, which is why insecticide-coated bed nets are so effective. Those who use bed nets are only half as likely to get malaria as those who do not. It is likely that within the next couple years, many African nations will have enough bed nets to cover their entire at-risk population.

In 2007, the World Health Organization announced its intentions to resume spraying DDT in malaria-endemic countries. Once the scourge of environmentalists, the chemical was banned in the late 1960s. However, it is still the most potent known insecticide. Many scientists now believe that DDT’s harmful effects may have been overstated, and in any case, eradicating malaria is a higher priority. The spraying of DDT to fight malaria is now supported by many prominent green groups, including the Sierra Club and Environmental Defense.

The cost of treating malaria victims is quickly dropping, offering hope that soon medication will be affordable to people in Sub-Saharan Africa. An initiative by European governments, called the Affordable Medicines Facility for Malaria, aims to reduce the cost of treatment through a combination of concessions and price reductions from pharmaceutical companies, subsidies from European governments, and donations from the private sector to reduce the cost of antimalarial medication to just 5 cents. The effort is already paying off; production of antimalarial medicine has risen from 5 million doses in 2004 to 160 million doses in 2009. Curing people quickly helps the victim and society alike; if people are quickly treated, mosquitoes will be less likely to acquire the malaria parasite each time they bite, and therefore less likely to transmit the disease to others.

Additionally, the search may finally be drawing to a close for the elusive malaria vaccine. In 2009 and 2010, scientists tested a vaccine among several hundred children in Mali. It proved to be effective at preventing malaria for at least one year, although additional tests will need to be conducted before the vaccine can be manufactured for public use.

The widespread use of bed nets, the resumption of DDT spraying, the increasing availability of treatment for victims, and the emergence of a possible vaccine are all coming together simultaneously to make it possible to rid the world of malaria once and for all.

Although the overall prevalence of malaria remains high, these figures mask an important insight: efforts to eradicate malaria are subject to a positive feedback loop. Once the number of infected people (or infected mosquitoes) drops below a certain threshold, it will be more difficult for additional people to become infected, which will reduce the number of infected people and infected mosquitoes even more. This will cause the malaria parasite population to crash, and can occur very quickly. The history of malaria in the United States is a good example of this. In the 1940s, malaria was still common in much of the southern United States, especially in the Mississippi Valley. In 1946, the Center for Disease Control was established with the explicit goal of eradicating malaria. A mere five years later, the disease was gone.

Will the World Health Organization be able to replicate this achievement in Africa, and meet the UN's goal of zero malaria deaths by 2015? I think that's a few years too optimistic. But due to the rapid reduction in malaria and the positive feedback loop which will aid eradication efforts, it isn't implausible. In 2005, the World Health Organization estimated that there were 350-500 million cases of malaria, but just a year later the number of cases had fallen to 247 million. By 2009, there were only 82 million cases. Such a rapid dropoff indicates that malaria is indeed in terminal decline. By the end of this decade, malaria can be rare or extinct, rather than the scourge that it is today.


By 2020 - There are fewer than 5 million cases of malaria annually, and fewer than 15,000 deaths.

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