How experts are interpreting the resurgence of malaria in the U.S

At least four locally transmitted cases of malaria were detected in Florida and Texas, the U.S. Centers for Disease Control and Prevention said. Malaria was considered eliminated in the U.S. in 1951, and no locally acquired cases have been reported in 20 years.

We’ve rounded up how experts are interpreting this resurgence.

• Scientists have worried that longer and warmer summers lead to more favorable conditions for malaria-infected mosquitoes, in part because heat speeds up the time it takes for parasites to mature inside mosquitoes. “So not only are these mosquitoes living longer, but they’re potentially becoming infectious sooner,” Oliver Brady, an associate professor at the London School of Hygiene and Tropical Medicine,” told CNN. The exact impact of climate change on the recent uptick in cases, though, is an open question, NPR reports.
• The new cases underscore the need for policymakers to ensure that the U.S. has sophisticated surveillance systems in place to detect cases more quickly, Dyann F. Wirth, an infectious disease professor at the Harvard T.H. Chan School of Public Health, told Politico Pulse. “If you miss a malaria case, it could have a serious consequence for the patient, not to mention for transmission,” Wirth said.
• Stopping a larger spread of malaria in the U.S. is “simple but not easy,” Wired reports. “Simple, because it requires only that people not bring the infection into the country.” But it’s not easy to control human movement, and thousands enter the U.S. from places where malaria is endemic, “whether as tourists, economic migrants, or asylum seekers and refugees.”
• No, this isn’t Bill Gates’ fault. Conspiracy theories posted to social media claimed that the Florida and Texas cases were linked to an initiative backed by Gates that involved releasing genetically modified mosquitoes in the U.S. But that biotech company doesn’t work with the kind of mosquitoes that transmit malaria. And the Bill & Melinda Gates Foundation doesn’t finance any such projects in the U.S., an Associated Press fact check found.

Most U.S. malaria cases are diagnosed after a person travels to a country where malaria is common and then returns home, according to the CDC. The locally transmitted cases happen after those infected humans are bit by domestic mosquitos, who then carry the virus and infect other people.

Globally, the number of malaria cases has risen in recent years, from 232 million in 2019 to 247 million in 2021, according to the World Health Organization. There were an estimated 619,000 deaths linked to malaria in 2021.