For the First Time in 20 Years, US Reports 7 Locally Acquired Malaria Cases

For the first time in 2 decades, the United States has locally acquired malaria infections. Six cases were confirmed in Florida and 1 in Texas, none related to international travel.

Additionally, the US Centers for Disease Control and Prevention (CDC) reported that the 2 states’ cases did not appear to be related. In Florida, the 6 cases were reported in Sarasota County, and active surveillance for additional infections is ongoing. Mosquito and infection surveillance and control are also underway in Texas, where 1 case was identified in a man working for the National Guard.

Malaria (Plasmodium vivax) is transmitted via the bite of an infected female anopheline mosquito. Malaria can be deadly, with nonspecific flu-like presentations including fever, chills, headache, myalgias, and fever, as well as nausea, vomiting, and diarrhea.

The initial 5 malaria patients have been treated and are clinically improving, the CDC stated. The health agency released an official Health Advisory on June 26 in response to the first confirmed infections.

The risk of malaria is very low, but with these 5 outlier infections, the CDC emphasized clinicians should consider malaria as a possible diagnosis for patients with a fever of unknown origin. The risk is higher in areas where climactic conditions enable the Anopheles mosquito to survive for the majority of the year. For suspected malaria patients, clinicians should order a rapid diagnostic test and microscopic examination of thick and thin blood smears.

In the US, an average of 5 people a year die of malaria, Healthline reported. Comparatively, in Africa, there were 594,240 malaria mortalities in 2021. The World Health Organization (WHO) estimates 619,000 people died of malaria in 2021, meaning Africa accounts for 96% of worldwide mortalities.

There is a malaria vaccine approved by WHO but it is designated for children aged 36 months–5 years in sub-Saharan Africa, who are at the highest risk for malaria-related death.

The last time locally acquired malaria occurred in the US was in 2003, when 8 cases of P vivax malaria were confirmed in Palm Beach County, Florida. Malaria was once endemic in the US, but implementing insecticides, drainage ditches, and window screens enabled it to be declared eliminated in 1951. Approximately 1500–2000 malaria cases are still reported in the US each year, but this is the first time in 20 years malaria was confirmed to be locally acquired, rather than contracted during international travel.

This is a developing story, and Contagion will provide updates as they become available. Catch up with our prior malaria coverage here.