Health: Death By Mosquito

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Recognition of malaria's toll on the global economy is growing. Economist Jeffrey Sachs, director of Columbia University's Earth Institute, estimates that countries hit hardest by the most severe form of malaria have annual economic growth rates 1.3 percentage points lower than those in which malaria is not a serious problem. Sachs points out that the economies of Greece, Portugal and Spain expanded rapidly only after malaria was eradicated in those countries in the 1950s. In other words, fighting malaria is good for business--as many companies with overseas operations have long understood. By the end of this year, Exxon Mobil, which plans to expand activities in the sub-Saharan countries of Chad, Cameroon, Angola, Equatorial Guinea and Nigeria, hopes to triple its funding for antimalaria projects and research, from $2 million to $6 million. But the malaria problem is bigger than Exxon Mobil or even Bill and Melinda Gates. Government action is needed.

To better understand why malaria has become such a threat and what can be done to stop the disease, it helps to know a little biology. Malaria is caused by four closely related parasites, the deadliest of which is Plasmodium falciparum, which has a particular fondness for anopheles mosquitoes. The parasites enter the bloodstream when an infected mosquito bites a human. Then they multiply inside the host's liver and red blood cells. (That's why pregnant women, who make lots of blood to nourish their growing fetus, are especially vulnerable.) Eventually the red blood cells burst with a new generation of parasites, causing fever, shivering, pain and sometimes death. The cycle of transmission is complete when another mosquito bites an infected person and picks up more parasites.

You might expect that one bout of malaria would lead to lifelong protection against the disease. But for complicated reasons, that is not the case. The illness tends to be less severe in adults who are continually exposed to the parasites. But when young children become infected, they are much more likely to suffer severe anemia and convulsions that may lead to permanent brain damage and death.

For decades, the best treatment for malaria was an inexpensive medication called chloroquine, first discovered in Germany in 1934 by a researcher working for Bayer. Chloroquine was so effective that it seemed it might vanquish malaria forever. But by the 1970s, the drug had been used so widely to treat all kinds of fevers, not just those caused by malaria, that the malaria parasites became resistant and doctors had to turn to a second medication, called sulfadoxine-pyrimethamine, or SP. But within five years, the parasites started to develop resistance to SP as well. Today resistance to both drugs is rampant in many parts of Africa, where resistant malaria parasites are the leading cause of death.