September 13, 2023
Medpage Today reports on a recent CDC recommendation for healthcare providers to consider malaria in diagnosis of patients with unexplained fever. This was in response to eight cases of locally transmitted malaria in Florida and Texas over the summer. Lab testing confirmed Plasmodium vivax parasites in the blood smears of all the cases. Public health departments in counties for each state sought CDC confirmation of suspected cases between May and July.
Both Florida and Texas experienced a single imported case prior to each locally transmitted case. Officials are still working to determine if the imported and locally transmitted cases in each state are linked but have found no evidence that the two outbreaks are linked. The CDC had also identified a locally transmitted case of Plasmodium falciparum malaria in Maryland earlier this year. None of the positive Florida or Texas patients had history of international travel, blood transfusion or organ transplant.
The CDC noted the risk for autochthonous malaria in the United States remains very low. The last outbreak of P. vivax malaria in the U.S. had occurred in 2003. Still, they recommended clinicians consider a malaria diagnosis in patients with an unexplained fever, especially in these areas where autochthonous malaria has been reported.
Following the identification of the first cases in Florida, the affected counties began mosquito control activities. This involved aerial and ground spraying of larvicides and deploying mosquito traps. The Florida Department of Health also worked with local partners to distribute insect repellant and bed nets to unhoused populations in the counties. Similar to Florida, Texas officials tested for possible spread after identifying the case there. Seven of the total cases resulted in hospitalization, though no one developed severe malaria or died.
In June, the CDC issued a Health Alert Network Health Advisory to notify clinicians, public health authorities, and the public about the cases. That was followed in July by a webinar to further educate clinicians on diagnosing and treating malaria.
PIDS member Audrey Odom John commented on the story, “Not that long ago, malaria was endemic across the U.S., especially in the South. Even when malaria was eliminated here, it has always been but a plane flight away. It’s unfortunate, but not terribly surprising, that it’s managed to get a toehold again. In many ways, we are lucky that it is Plasmodium vivax, which typically causes a less severe form of malaria. Since vivax can hide out in the liver, however, clinicians need to be aware that there may be patients that didn’t know they were infected and show up months later with fever, even after this mini-outbreak has quieted down.”