Native instances of malaria have been confirmed in the US: ought to I be involved?


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At least four people in Florida and one in Texas have been diagnosed with malaria which they must have caught close to home, because, according to health officials, none of them traveled outside the United States or their own state. This highly unusual finding has left infectious disease specialists wondering: Who else might be sick and will local doctors recognize what’s wrong?

Malaria is not completely unprecedented in the United States: about 2,000 people get it every year, but almost always because they have traveled to a place where it is endemic, been bitten by an infected mosquito there and fell ill after returning home. Locally acquired malaria is extremely rare. It stems from a chain of transmission that likely begins with an American mosquito biting a tourist, migrant or refugee who has been in an endemic country and carries the infection in their blood. Then the insect transmits it by biting someone else. This hasn’t happened in the United States since 2003.

There are approximately 247 million cases of malaria worldwide each year, according to the World Health Organization, and in each of them, a mosquito is just the vector. Humans are the natural host of the disease; mosquitoes carry it between people. (Contrary to with covid and some other diseases, animals play no role.) So when experts hear that someone has been diagnosed and can be sure that person has not travelled, their first impulse is to ask, « Who another was infected but not found? ? »

“If there are five cases right now, that means there must be a lot more infected mosquitoes,” says Ross Boyce, physician and assistant professor at the University of North Carolina at Chapel Hill School of Medicine. who runs a malaria research program in Uganda. « And there may even be more people infected than we know at this point. »

The five people identified by health officials, in Sarasota County on Florida’s west coast and Cameron County on the southern tip of Texas, have already received treatment and are recovering, according to the Centers for Disease Control and Prevention. (CDC). In both areas, mosquitoes have been trapped and analyzed, and mosquito control districts are spraying insecticides to bring down local populations.

These are familiar actions in parts of the United States, as they were essential to defend against the Zika outbreak which swept across North and South America in 2016 and landed in Brownsville, Texas, in Cameron County, at the end of this year. Florida has been battling outbreaks of dengue fever, another mosquito-borne virus, for more than a decade after appeared in Key West then moved north of miami.

But malaria has not been persistently present in the United States since it was eliminated here in 1951, in a campaign that gave birth to the CDC. (The agency was originally called the War Zone Malaria Bureau, tasked with reducing the disease’s impact on soldiers traveling to World War II battlefields and bases producing tanks and ships.) So malaria experts worry that doctors, especially primary care doctors, might not know it when they see it.


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