IStock Photo 1150402 © Michael Pettigrew

It’s annoying to hear the high, thin whine of a mosquito just as you’re falling asleep and realize that you may wake up scratching. On the upside, you have virtually no chance of contracting malaria—not if you live in the United States, anyway.

Yet, worldwide, this mosquito-borne disease kills at least one million people every year, mainly in developing countries. No vaccine exists yet, although pharmaceutical giant GlaxoSmithKline (GSK) is testing one in Africa. In an unusual step, GSK also pledged on Jan. 20, 2010 to make data on 13,500 compounds that may inhibit malaria available online without charge as a way to encourage further research.

Malaria was endemic across the US through World War II. Now, however, the odds that a person will be diagnosed with malaria in a year in the US are 1 in 203,100. For comparison, the risk of visiting an emergency room due to an accident involving a toothbrush in a year are twice as high (1 in 99,340).

European settlers brought malaria (from the Italian for “bad air”) across the Atlantic, and pioneers carried it west across North America. Until British scientist Ronald Ross showed in 1897 that the disease was carried by a mosquito parasite, Americans knew little about it. (In Little House on the Prairie, Laura Ingalls Wilder’s family falls ill with “fever ’n ague,” which they think came from breathing night air or eating watermelons. The real problem was that those melons grew in swampy, mosquito-infested Kansas creek bottoms.)

Malaria infected thousands of Americans through the early 20th century, and was especially widespread in the South. When the Tennessee Valley Authority was created in 1933 to promote economic development in the South, the odds that a person living in the TVA region was affected by malaria were one in 3.33. Aggressive measures, including widespread spraying with a new insecticide called DDT, virtually wiped out the disease in TVA states by 1947. By the early 1950s malaria was considered to have been eradicated across the United States.

Today Americans are only at serious risk of catching malaria if they travel to places where it’s still endemic, like Africa or Latin America. Worldwide, 41 percent of the world’s population lives in parts of Africa, Asia, the Middle East, Latin America, and Oceania where malaria is present, and more than one million people die from the disease every year.

Travelers can guard against malaria by taking antimalarial drugs (4 species of mosquito spread the disease, so medications vary by destination). Staying indoors, wearing protective clothing outdoors, and using insecticide help prevent mosquito bites. Anyone who develops fever or a flu-like illness after visiting a region where malaria is present should seek medical help right away.

Celebrities including Bono, David Beckham, and Ashley Judd have endorsed a new campaign called United Against Malaria that aims to provide insecticide-treated mosquito nets and malaria medicines throughout Africa by the end of 2010 (a goal set by the United Nations). Jamie Drummond, executive director of the charity group One, calls it “unforgivable . . . that in the 21st century a child should die from a mosquito bite.”