, the Centers for Disease Control and Prevention says.
The federal health agency recently issued a nationwide warning to health providers and officials to be on the lookout for symptoms of the potentially fatal illness. Usually, people in the U.S. who get malaria get the disease during international travel.
All five people – four in Florida and one in Texas – have received treatment and are improving, according to the CDC. The case in Texas is not related to the Florida cases, and all occurred in the past 2 months.
Malaria cannot be transmitted from person to person. It is spread by the bite of an infected female mosquito. The last cases of people being infected while in the U.S. occurred 20 years ago, when there were eight cases in Palm Beach County, Fla. The Texas Department of State Health Services said the last time malaria was locally acquired in the state was 1994.
The Florida Department of Health said it was spraying for mosquitoes in the two counties surrounding Sarasota, Fla., where the four cases occurred.
The CDC said the risk of getting malaria while in the United States “remains extremely low.” The agency advised people to protect themselves by taking precautions to prevent mosquito bites, such as wearing insect repellent and wearing long-sleeved shirts and pants. People should also do things to ensure that mosquitoes aren’t around their home, such as getting rid of standing water, which is an environment for mosquitoes to lay eggs.
More than 240 million malaria cases occur annually worldwide, the CDC said, with 95% in Africa. There are 2,000 cases diagnosed annually in the U.S. that are related to international travel. Malaria symptoms are similar to those of other illnesses and include fever, chills, a headache, and muscle aches. If not treated, malaria can be fatal.
A version of this article first appeared on WebMD.com.