Florida sees first local transmission of malaria since 2003

Mosquito-borne illnesses
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3 min read

Dear Doctors: I was surprised to read that there have been several cases of locally acquired malaria diagnosed near my home in Florida. I didn't realize that we still have malaria in the United States. Is it widespread? I would appreciate information about symptoms to look out for.

Dear Reader: Malaria is a serious -- and potentially deadly -- mosquito-borne illness. The malaria pathogen is a single-celled blood parasite that belongs to the genus Plasmodium. It enters the body via the bite of a female Anopheles mosquito. Only female mosquitos, who need a blood meal in order to produce eggs, bite their prey. Male mosquitos don't bite and don't transmit disease.

Of the 100-plus species of Plasmodium, five are known to infect humans and cause malaria. Once in the blood, they reproduce rapidly, shedding waste and other byproducts. These toxic substances damage and destroy red blood cells, which leads to the symptoms of malaria.

Malaria typically causes flulike symptoms, including fever, chills, shivering, headache, muscle and body aches and exhaustion. Some people experience gastrointestinal symptoms, including nausea, vomiting and diarrhea. Destruction of red blood cells often leads to anemia. And because the parasite takes up residence in the liver, jaundice, which is yellowing of the skin and the whites of the eyes, is common.

How serious someone's case of malaria can become depends on the specific species of Plasmodium causing the infection.

When a patient's symptoms, along with their travel history, suggest a diagnosis of malaria, a blood sample will be obtained for laboratory testing. If Plasmodium is detected, treatment with drugs to kill the parasite, known as antimalarials, will begin. The specific drug that is used depends on the species of parasite that has been identified. Some strains of Plasmodium have become resistant to antibiotics, which necessitates the use of combinations of drugs to manage the infection.

If left untreated, infection can become severe. Malaria can lead to cognitive lapses, kidney failure, severe anemia, seizure, coma and death.

Malaria was widespread in the U.S. for centuries. Thanks to nationally coordinated mosquito abatement policies, along with the advent of window screens, the disease was deemed eradicated in the 1950s. The 2,000 cases now diagnosed in the U.S. each year are largely acquired during travel.

However, as you point out, a handful of cases acquired in the U.S. have recently been diagnosed. Seven of those were located in Florida, and one was in Texas. All of the patients have been successfully treated for the disease. These are the first known cases of local transmission since 2003, when nine cases were identified in the Palm Beach area of Florida.

This newest cluster of malaria cases has caused the Centers for Disease Control and Prevention to notify health care providers and public health authorities via a national health advisory. Meanwhile, travelers to regions where malaria is endemic are urged to take all possible precautions. This includes wearing protective clothing, using insect repellent, sleeping under mosquito netting and taking a protective regimen of antimalarial drugs.

(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

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