Diagnosing, Treating, and Preventing Malaria in the United States

Although local spread of malaria within the United States (US) is rare, 10 locally acquired cases in Arkansas, Florida, Maryland, and Texas were reported in 2023.¹ Malaria is considered a medical emergency by the Centers for Disease Control and Prevention (CDC), and as such, prompt diagnosis and treatment is essential, said Dottie Borton, BSN, RN, CIC, FAPIC, in an article in Nursing, which detailed strategies for preventing the spread of malaria in the US.²

Malaria is preventable with rapid identification and treatment. It is caused by the protozoan Plasmodium parasite that infects macaques in Southeast Asia and is transmitted to humans through bites by infected Anopheles mosquitos. An estimated 249 million cases of malaria in 85 countries occurred in 2022 and 608,000 people, mostly children, died from malaria infections.³

Before 2023, the last known case of locally acquired malaria in the US was in 2003. The 10 local cases in 2023 were neither related to travel to malaria-endemic regions nor were they related to each other. Nine cases were caused by Plasmodium vivax (P vivax) and 1 case was caused by Plasmodium falciparum (P falciparum), according to the CDC.

Since the 1970s, rates of malaria have been increasing in the US, said Borton. In a typical recent year, more than 99% of the approximately 2000 malaria cases reported in the US are associated with travel. Of these, approximately 300 cases progress to severe disease, and between 5 and 10 individuals die from the infection, Borton said.

Prevention

Most individuals who contract travel-related malaria did not follow recommended prophylaxis before and during travel or they chose to use homeopathy, Borton said.

To prevent malaria, individuals traveling to endemic regions should complete the full course of prophylaxis treatment. Information on endemic areas by country can be found on the CDC website. Prophylaxis options include atovaquone or proguanil, chloroquine, doxycycline, mefloquine, primaquine, and tafenoquine. The selection of therapy should consider the patient, as some should not be given to children or pregnant women, and the travel destination, as some regions have resistant Plasmodium endemic to those areas.

Once a traveler has reached their destination, individuals should be advised to continue with their prophylaxis and to avoid mosquito bites, use screens in doors and windows, sleep under a mosquito net treated with an insecticide, wear appropriate clothing and apply permethrin-containing products to clothes, and to use insect repellant with N,N-diethyl-meta-toluamide (DEET); picaridin; IR3535; or lemon eucalyptus oil, Borton said.

Diagnosis

Anyone who is bitten by a mosquito infected with Plasmodium can develop malaria. Individuals at the highest risk for severe malaria received multiple bites from infected mosquitoes and/or have no malaria immunity, Borton said.

The incubation period of malaria ranges by Plasmodium species, from 6 to 14 days for P falciparum to as long as 18 to 40 days for Plasmodium malariae. Both P vivax and Plasmodium ovale (P ovale) can be dormant in the liver and relapse if untreated.

Malaria infection presents with nonspecific symptoms that are similar to those of influenza, such as fever, chills, headaches, myalgia, cough, tachypnea, nausea, vomiting, and diarrhea. Severe malaria can present with altered mental state, seizure, severe anemia, respiratory distress, severe fatigue, jaundice, renal failure, dark urine, and multiorgan failure.

Malaria should be considered for patients with unidentified febrile illness, especially with a travel history to an endemic region within the last 12 months. Patients suspected of malaria infection should be evaluated urgently for signs and symptoms, a travel history should be collected, and laboratory testing should be performed within 24 hours.

The gold standard malaria test is Giemsa stained thick and thin blood smear microscopy. Thick blood smears show the presence of malaria parasites whereas thin blood smears show parasite morphology to determine the Plasmodium species.

Clinicians may also choose to use rapid diagnostic tests (RDTs) for the malaria antigen to reduce testing time, however, RDT results should be confirmed with blood smear microscopy and cannot be used to determine Plasmodium species.

Treatment

After a patient is diagnosed with malaria, hospitalization is recommended for patients in the US, because individuals who do not live in endemic regions and do not have preexisting immunity are at risk for severe disease.

Oral antimalarial medications should be administered to patients with malaria immediately. The choice of antimalarial medication is based on the Plasmodium species. For uncomplicated, nonsevere P falciparum infections, the first-line treatment choice is artemether-lumefantrine. Most non-P falciparum malaria cases respond to chloroquine or hydroxychloroquine. For infections with P vivax or P ovale, additional treatment with primaquine or tafenoquine is needed to eradicate the infection from the liver and prevent relapse.

For severe malaria cases, patients should be admitted to the intensive care unit and receive immediate treatment with intravenous artesunate, which is effective against all Plasmodium species. Response to therapy should be monitored by repeated thick and thin blood smears every 12 to 24 hours. Patients should be switched to a full course of oral therapy after the parasite density is reduced to <1%, Borton said.

All malaria cases should be reported to the state, territorial, local, and/or tribal health departments. An urgent infectious disease consultation is recommended for all malaria cases in the US. Public health authorities and the CDC are available for consultation if needed.

For more information regarding the malaria surveillance system, or assistance in completing the form, please call the Malaria Branch at 770-488-7788 or toll-free at 855-856-4713.

The CDC provides a graphic Malaria is a Serious Disease that can be used to educate patients.