Mosquitoes in many places in the world including South Asia and Sub-Saharan Africa carry Plasmodium parasites, which cause malaria. In the past several months, health officials confirmed that four people in Florida and one person in Texas have been infected with malaria. These cases were not tied to international or interstate travel, making them among the first locally acquired cases of malaria in a US state in twenty years. Decades ago, the US undertook a huge malaria eradication campaign that was primarily accomplished by spraying copious amounts of DDT anywhere the parasite-carrying mosquitoes lived.
According to the Centers for Disease Control and Prevention (CDC), about 2,000 people are diagnosed with malaria in the US annually. However, those people acquire malaria during travel overseas to places where the disease is far more common. In the past ten years, only one other locally acquired case of malaria has been confirmed in Florida besides these recent two.
Researchers are still learning about how these cases arose. It's possible for a person to bring malaria home to the US from a trip, then if they are bitten by a mosquito, that mosquito is then infected with the parasite. That infected insect can then go around biting people, potentially infecting others with a Plasmodium parasite.
In the Sarasota area, where the Floridians were infected, health officials confirmed that Plasmodium-infected mosquitoes were found in a local swamp. Insecticides are being applied to kill adult and juvenile mosquitoes there.
Right now, officials are not sounding any alarms. But these cases are a reminder that mosquitoes can present serious threats, and it's best to try to avoid bites if possible.
There are a few species of Plasmodium that can cause malaria. If there is any silver lining to this news, its that the cases were caused by the P. vivax type, which does not cause the worst malaria cases. The P. falciparum parasite is the deadliest type of Plasmodium, and it's thought to be about ten times more deadly than P. vivax.
Milder symptoms of P. vivax can include flu-like symptoms such as stomach problems and fever. The parasite can also infect a person and then hang out in the liver, where it may lie dormant for many years until it causes a severe infection later.
The World Health Organization (WHO) has estimated that in 2021, around 247 million people got malaria and 619,000 died.
A malaria vaccine called Mosquirix or RTS,S/AS01 (RTS,S) has been shown to reduce severe malaria in children, and is credited with lowering child deaths in a few countries in Africa where it was tested. It takes four injections, and is effective for about 75 percent of people who are treated. There is a second malaria vaccine called R21/Matrix-M (R21) being tested now.
