Recent Cases of Human Malaria in the United States
An image of a common malaria mosquito. This mosquito is found throughout much of the eastern United States. Other malaria mosquitoes can also be found in the U.S. Photo credit: Lauren Bishop and Amy Lockwood, Centers for Disease Control and Prevention
During the week of August 18, 2025, the New Jersey Department of Health (NJDOH) and the New Jersey Department of Environmental Protection reported that a human tested positive for malaria in New Jersey. While there are hundreds of travel-related malaria cases each year in the United States, this case is notable because this person had no history of traveling outside the United States, indicating that this may have been a locally acquired malaria case (Centers for Disease Control and Prevention [CDC], 2025a; NJDOH, 2025).
Why is this important?
Pennsylvania and other states with large international airports may occasionally have cases of travel-related malaria, meaning that people have traveled to areas where malaria-causing parasites and the mosquitoes that can transmit them live (CDC, 2024a, 2025b). These people become infected with the parasites and then become sick after returning to the United States. Since the affected person in New Jersey had no known history of leaving the United States, they may have been locally infected with malaria. This would be the first known local malaria case in New Jersey since 1998 (NJDOH, 2025). Endemic or local cases of malaria indicate that the malaria-causing parasite has been reintroduced into a mosquito population in New Jersey.
How do the parasites that cause malaria spread?
Human malaria is caused by a Plasmodium parasite that lives in mosquitoes and humans during different portions of its life cycle (CDC, 2024a). The mosquitoes that can transmit parasites that cause human malaria are commonly called malaria mosquitoes and are in the genus Anopheles. Local cases of malaria usually happen when a person who is infected with malaria-causing parasites returns from traveling and is bitten by a mosquito in the United States (NJDOH, 2025). That mosquito becomes infected with the parasite as it draws blood from the infected person. When an infected mosquito feeds again, it can infect another person who may live nearby with the parasites. If that same mosquito bites another person, they may also become infected. Other local, uninfected mosquitoes may bite people infected with the parasites and continue this local transmission cycle.
Malaria prevention
Malaria prevention starts with mosquito bite prevention (CDC, 2024b). Reduce your risk of mosquito bites by wearing long-sleeved, loose-fitting clothing. Mosquitoes can bite through tight-fitting pants and shirts. Clothing can also be treated with permethrin, which will help repel both mosquitoes and ticks. Applying EPA-registered insect repellents to the skin before heading outside can also act as another barrier to mosquitoes. These same tips can be used to help reduce the chance of mosquito bites when traveling to areas with malaria and other mosquito-borne diseases.
To help prevent mosquitoes from breeding near your home, dump out bird baths, buckets, and other small water sources at least once per week. Remove any plastic containers or toys that are collecting water from your yard. Consider using mosquito larvicides such as Bti dunks for larger water sources such as ponds and other water features. Remember to read and follow the label of any repellents and pesticides you use. Clean and maintain rain gutters and other areas where water may collect if you can. Make sure to install and use window and door screens if you leave windows and doors open to enjoy the fresh air. Inspect window and door screens yearly to ensure no holes are present. Â
Conclusion
While local malaria cases can be and are concerning, the chances of them happening can be reduced by following personal protective measures, such as using EPA-registered repellents while travelling. When mosquito-borne disease cases occur, we can help reduce their chance of spreading further by using those same personal protective measures at home and following the above tips to help prevent mosquitoes from breeding nearby or entering the house.
More Resources
Malaria: A Brief History in the United States Penn State Extension
Tick and Mosquito Repellent Guide Penn State Extension
Using Insect and Tick Repellents Safely Penn State Extension
References
Centers for Disease Control and Prevention. (2024a, March 12). How malaria spreads. Retrieved August 29, 2025.
Centers for Disease Control and Prevention. (2024b, August 28). Preventing mosquito bites. Retrieved September 12, 2025.
Centers for Disease Control and Prevention. (2025a, May 27). Data and statistics on malaria in the United States. Retrieved September 12, 2025.
Centers for Disease Control and Prevention. (2025b, May 28). Malaria surveillance, United States, 2022. Retrieved September 12, 2025.
NJ Department of Health. (2025, August 18). NJDOH and NJDEP Investigate Case of Malaria in Morris County Resident with No Recent International Travel [Press Release].
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.
