There have been 5 reported cases of locally transmitted malaria; 1 in Texas and 4 in Florida, according to a Health Advisory released by the Centers for Disease Control and Prevention (CDC).

The CDC noted that there is no evidence that the cases in the 2 states are related.  “In Florida, 4 cases within close geographic proximity have been identified, and active surveillance for additional cases is ongoing. Mosquito surveillance and control measures have been implemented in the affected area. In Texas, 1 case has been identified, and surveillance for additional cases, as well as mosquito surveillance and control, are ongoing,” said the CDC.

The last report of locally acquired malaria was in 2003 when 8 cases of Plasmodium vivax malaria were identified in Palm Beach County, Florida. The CDC emphasized that malaria is a medical emergency and should be treated accordingly. “Patients suspected of having malaria should be urgently evaluated in a facility that is able to provide rapid diagnosis and treatment, within 24 hours of presentation,” said CDC.

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CDC Recommendations for Clinicians

Clinical manifestations of malaria are non-specific and include fever, chills, headache, myalgias, and fatigue. Nausea, vomiting, and diarrhea may also occur. For most people, symptoms begin 10 days to 4 weeks after infection, although a person may feel ill as early as 7 days or as late as 1 year after infection.

When examining a patient with a high fever of unknown cause, clinicians should:

  • Consider the diagnosis of malaria, regardless of international travel history, particularly if they have been to areas with recent locally acquired malaria.
  • Routinely obtain a travel history and consider malaria in a symptomatic person who traveled to an area with malaria in the weeks to months preceding symptom onset.

Treatment Recommendations

Since malaria is an infrequently encountered condition, the CDC is urging clinicians to refer to CDC’s Malaria Diagnosis and Treatment Guidelines for specific detailed instructions. Malaria is caused by any of 5 species of protozoan parasite of the genus Plasmodium: P falciparum, P vivax, P malariae, P ovale, and P knowlesi. If not diagnosed and treated promptly, malaria may progress to severe disease, where mental status changes, seizures, renal failure, acute respiratory distress syndrome, and coma may occur. Approximately 2000 cases of mostly travel-related malaria are diagnosed in the United States each year; approximately 300 people experience severe disease (most from P falciparum), and 5 to 10 people with malaria died yearly.

Patients suspected of having malaria should be evaluated quickly in an emergency facility that can provide rapid diagnosis and treatment within 24 hours of presentation. Malaria is diagnosed through a blood smear using a rapid diagnostic test (RDT) if available. The CDC noted that BinaxNOW™, a malaria RDT, is approved for use in the United States. RDTs are less sensitive than microscopy and cannot confirm each specific species of the malaria parasite or the parasite density. Therefore, microscopy should also be obtained in conjunction with an RDT as soon as possible, noted the CDC.

The preferred treatment for malaria is artemether-lumefantrine (Coartem) for the initial treatment of uncomplicated P. falciparum or unknown species of malaria acquired in areas of chloroquine resistance. Atovaquone-proguanil (Malarone) is another recommended option.

P. vivax infections, like the ones diagnosed in the US, should initially be treated with chloroquine (or hydroxychloroquine).

IV artesunate is the first-line drug for the treatment of severe malaria in the United States. Artesunate for Injection is approved by the FDA for treating severe malaria and is commercially available.

Species determination is important because P vivax and P ovale can remain dormant in the liver and require additional treatment; failure to treat the dormant hepatic parasites may result in chronic infection with relapsing episodes. Relapses may occur after months or even years without symptoms.


Centers for Disease Control and Prevention. Locally Acquired Malaria Cases Identified in the United States. Accessed June 28, 2023.

Mace KE, Lucchi NW, Tan KR. Malaria Surveillance — United States, 2018. MMWR Surveill Summ. 2022;71(No. SS-8):1-29.

Centers for Disease Control and Prevention. Intravenous Artesunate for Treatment of Severe Malaria in the United States. Accessed June 28, 2023.