Maryland reports first locally acquired malaria infection in 40 years

A Maryland resident was hospitalized with malaria after contracting the disease locally — a first in more than 40 years, Maryland Department of Health officials said Friday.

Malaria is caused by a parasite transmitted through mosquito bites. The Health Department did not say precisely where the patient was exposed to malaria, but officials said the person lives in the National Capital Region, which includes Prince George’s, Montgomery, Charles and Frederick counties. The patient, who was not identified by age or gender, has been discharged and sent home to recover, officials said.

“Malaria can be very dangerous and even fatal if it is not treated, but early treatment reduces the chances of complications,” Deputy Secretary for Public Health Services Nilesh Kalyanaraman said in a statement. “We urge the public to take precautions against mosquito bites, and if you develop symptoms after traveling abroad, seek urgent medical care.

Locally contracted malaria cases have also been reported in Florida and Texas this year for the first time in decades, raising concerns that the disease could return to areas where it has long been considered eradicated. Malaria was declared “eliminated” in the United States in 1951, and the World Health Organization designated the country “malaria free” in 1970. Some scientists have warned that rising temperatures caused by climate change may help spread malaria by expanding the mosquito’s natural territory, something a recent study showed is already happening in parts of Africa.

The locally transmitted case in Maryland reported Friday came from a different strain of parasite than the recent cases in Florida and Texas, a Health Department official said. The Maryland case was caused by a parasite called P. falciparum, while the cases in Florida and Texas came from a parasite called P. vivax.

People can prevent mosquito bites by using an insect repellent that contains DEET, wearing loosefitting, long-sleeved clothing, closing windows and doors or covering them with screens, and emptying standing water at least once a week to prevent mosquitoes from laying eggs.

Malaria symptoms typically appear seven to 30 days after a bite from an infectious mosquito, the state Health Department said. Patients may develop fever, chills, headache, body aches and fatigue. Anyone experiencing those symptoms who may have been exposed to malaria should seek urgent medical care, officials said.

Maryland typically reports about 200 travel-related cases of malaria each year, and there are more than 2,000 cases reported in the United States annually, but for decades all of those cases occurred in people who had recently visited areas of the world where the disease is more common.

The current risk of malaria in the U.S. is very low, CDC spokesperson Kathleen Conley said in an email, adding that the agency’s national malaria system “works quickly and effectively to identify cases of malaria and connect patients to treatment.”

Maryland has long been home to the Anopheles mosquito, which can spread the parasite that causes malaria from person to person. David Blythe, director of the Maryland Department of Health’s Infectious Disease Epidemiology and Outbreak Response Bureau, said the state had eradicated locally contracted infections because of mosquito control efforts that significantly reduced the public’s exposure to the Anopheles mosquito.

Blythe said one way malaria could be reintroduced to Maryland is by someone who contracted the parasite in another country and brought it back to the state. If a local mosquito bit that person in Maryland and then bit a second person, it could spread the parasite.

Travelers who know they could be exposed to malaria-spreading mosquitoes in another country can get preventive drugs from their physician to reduce the chances that they contract the disease and spread it to others.

This story has been updated to include comment from the CDC.