U.S. malaria cases are at their highest level in four decades, mostly from Americans bringing home an unwelcome souvenir from their travels.
Malaria is not a big problem in the U.S.—there were only 1,925 cases in 2011, including five deaths. But cases were up 14 percent from the previous year, and the most since 1971.
Nearly all the cases were Americans or foreign travelers bringing it into the country. About two-thirds were infected in Africa, where malaria is common.
Malaria is a deadly tropical disease spread by mosquitoes. It's treatable when caught early.
Travelers can protect themselves by taking malaria drugs before and during a trip. Only a fraction of the 2011 cases took the right drugs.
Health officials released the numbers Thursday.
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