Portrait of a killer

The disease: Malaria in humans is caused by single-celled parasites. When a mosquito bites an infected person, it ingests the parasites and can pass them on to another person. Malaria can be fatal but is curable if diagnosed and treated promptly.

Prevalence: About 2.4 billion people in 90 countries— 40 percent of the world's population—are exposed to the disease. There are 300 million to 500 million clinical cases reported each year, more than 90 percent of them in sub-Saharan Africa. About 1,200 cases are diagnosed in the United States each year, most of them in immigrants and travelers returning from Africa and India.

Mortality: Malaria is estimated to kill more than 1 million people annually — mostly children in remote, rural areas.

Symptoms: Malaria can produce a fever and flu-like symptoms, including chills, headache, muscle aches and fatigue. The disease can cause anemia and jaundice and might cause kidney failure, coma and death. Symptoms usually begin 10 days to four weeks after infection.

Prevention and treatment: Community prevention meas.ures include eliminating mosquito breeding areas with insecticides and draining swamps and marshy areas. Personal prevention measures include anti-malarial drugs and bed netting treated with insecticide. The disease is curable with prescription drugs.

Information: More information about malaria is available from the Multilateral Initiative on Malaria (mim.nih.gov), the Centers for Disease Control and Prevention's National Center for Infectious Diseases (www.cdc.gov/ncidod) and the World Health Organization (www.who.int).

Sources: World Heath Organization and National Center for Infectious Diseases