Malaria

This infectious disease is caused by single-celled Plasmodium protists, including P. falciparum, P. vivax, P. malariae, and P. ovale. The parasites are usually transmitted from infected to noninfected people via the bite of female Anopheles mosquitoes; about 60 species of Anopheles can serve as vectors. The parasites take up residence in the victim's red blood cells.

The disease is characterized by episodes of chills and fever followed by profuse sweating; shaking and fatigue are other common symptoms. Repeated bouts can result in severe anemia, dehydration, and death. Infants, children, and pregnant women are at greatest risk of severe illness and death.

Treatment with chloroquine or other drugs that kill the Plasmodium has become more difficult in recent years. The parasites have become resistant to the drugs, and the Anopheles mosquitoes have become resistant to insecticides. Efforts to produce a malaria vaccine have been extensive but unsuccessful.

Malaria is most common in tropical and subtropical lands, particularly sub- Saharan Africa and Southeast Asia. It is both a cause of poverty and a result of poverty. Each year, between 300 million and 500 million acute cases are diagnosed and 1.5 million to 2.7 million people die of the disease. Almost all of the approximately 1,000 Americans who contract malaria each year get the disease while traveling abroad.