Malaria: A Brief History in the United States

What Is Malaria?

Malaria is a potentially deadly disease caused by several species of Plasmodium parasites. Different species of Plasmodium are found across much of the world, but not all can be transmitted to humans. The Plasmadoium species that cause malaria in humans may be transmitted via the bite of an infected Anopheles mosquito. To complete its lifecycle, certain stages of the human malaria-causing parasite must live in a human, and certain stages require a mosquito host to develop (CDC, 2024a).

Malaria symptoms usually appear within two weeks after a bite from an infected mosquito but can sometimes take months before appearing. The severity and timing of malaria symptoms can vary based on the type of Plasmodium parasite contracted. Common symptoms include fevers, chills, sweating, headaches, vomiting, body aches, and nausea. Certain Plasmodium parasites may cause symptoms to relapse or reappear after weeks to years if left untreated or uncured. Severe symptoms may lead to death, but there are treatments for malaria, and it can be cured (CDC, 2024c; CDC, 2024d). Talk with your medical provider for a diagnosis of any symptoms.

Has Malaria Ever Been Common in the United States?

Malaria cases were common across much of the United States through the late 1800s, including throughout the East Coast, Gulf states, and from the Midwest states west to Texas and Montana (Zucker, 1996). During the early to mid-1900s, the area where malaria cases occurred within the United States shrank to southern states (Zucker, 1996). By the 1950s, the United States was declared malaria-free (Pan American Health Sanitary Bureau, 1969). Malaria transmission was eliminated in the United States due to improved sanitation and widespread mosquito control efforts (Zucker, 1996). Controlling and reducing mosquito contact with humans interrupted the transmission cycle of malaria-causing parasites within the United States. Cases of malaria continued to occur in the United States after this period. However, most of these cases were travel-related (Zucker, 1996). A travel or imported case is when a person travels to an area where malaria-causing parasites and mosquito vectors are present and becomes infected before returning home, where they begin to show symptoms and are diagnosed. A locally acquired malaria case is when an infected mosquito bites a person and contracts malaria-causing parasites within their home state or country. Today, most locally acquired malaria cases are concentrated across much of the tropics (World Health Organization, 2023).

Is Malaria Still Common in the United States?

Local human malaria cases in the United States have happened in recent decades, including multiple outbreaks between 2000 and 2003 and as recently as 2023 in Texas, Florida, and Maryland (Blackburn, 2023; Dye-Braumuller & Kanyangarara, 2021). The mosquitoes that can transmit malaria-causing parasites in the United States still exist and can contract malaria-causing parasites from recently infected travelers returning home. As shown by the local cases happening in recent years, the potential exists for malaria-causing parasites to begin circulating locally within the United States if Anopheles mosquitoes bite infected travelers. Pennsylvania reports 60 counties with types of Anopheles mosquitoes that could carry and transmit malaria-causing parasites and contains one of the most traveled international airports in the United States, where travelers may directly travel to and return from areas that contain malaria-causing parasites (Dye-Braumuller & Kanyangarara, 2021). Locally acquired cases in the United States in 2023 highlight the importance of preventing mosquito bites when traveling and at home.

How Can I Protect Myself?

The locally acquired malaria cases in the United States in 2023 emphasize the need for continued awareness of malaria in the United States and worldwide. Take proper precautions to avoid mosquito bites at and around the home, including applying EPA-registered repellents, wearing long-sleeved, loose-fitting clothing, treating clothing with permethrin, tipping stagnant water around the house, and maintaining window and door screens. Preventing mosquito bites at and around the house will also help to protect you from other vector-borne diseases such as West Nile virus or eastern equine encephalitis.

Travelers leaving the United States should be aware of any vector-borne diseases, including malaria, that might be common in the areas they intend to visit. When traveling, continue to wear insect repellents and use other personal protective measures such as wearing long-sleeved, loose-fitting clothing to avoid bites from vectors of diseases. Depending on the location, duration, and activities you plan when traveling, a healthcare provider may be able to prescribe malaria preventatives (CDC, 2024d). Other mosquito bite prevention methods should be used even when malaria preventatives are used. When returning to the United States, travelers should be aware of any symptoms and talk with their medical provider as soon as they appear.

References

Blackburn, D. (2023). Outbreak of locally acquired mosquito-transmitted (autochthonous) malaria—Florida and Texas, May–July 2023. Morbidity and Mortality Weekly Report, 72. 

Centers for Disease Control and Prevention. (2024a, March 12). How malaria spreads. U.S. Department of Health and Human Services.

Centers for Disease Control and Prevention. (2024b, April 11). Preventing malaria while traveling. U.S. Department of Health and Human Services.

Centers for Disease Control and Prevention. (2024c, May 17). Symptoms of malaria. U.S. Department of Health and Human Services.

Centers for Disease Control and Prevention. (2024d, April 25). Treatment of malaria. U.S. Department of Health and Human Services.

Dye-Braumuller, K. C., & Kanyangarara, M. (2021). Malaria in the USA: How vulnerable are we to future outbreaks? Current Tropical Medicine Reports, 8(1), 43–51. 

Pan American Health Sanitary Bureau, Regional Office of the World Health Organization. (1969). Report for the registration of malaria eradication from the United States of America.

World Health Organization. (2023). World malaria report 2023. World Health Organization.

Zucker, J. R. (1996). Changing patterns of autochthonous malaria transmission in the United States: A review of recent outbreaks. Emerging Infectious Diseases, 2(1), 37–43.

Disclaimer: This project was supported by Cooperative Agreement Number NU50CK000637 from the Centers for Disease Control and Prevention. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention.