First Likely Case of Locally Acquired Malaria in Washington State

In a rare and significant development, a woman from east Pierce County has been diagnosed with malaria despite not having traveled outside of Washington recently. The diagnosis was confirmed on Saturday, August 2, by the Tacoma-Pierce County Health Department, and she is currently undergoing treatment. This case raises the possibility of a locally acquired malaria infection within the state, which would mark the first such incidence in Washington and potentially the first reported case of malaria contracted west of the Rocky Mountains.

Health officials are actively investigating the source of the infection, with collaboration between the county health department, the Washington State Department of Health, and the Centers for Disease Control and Prevention (CDC). One of the primary efforts includes trapping and testing local mosquito populations to determine if they are the carriers of the disease.

Malaria is a mosquito-borne illness that typically causes symptoms such as fever, chills, body aches, headaches, and fatigue. If left untreated, it can be fatal. However, it is treatable with specific antimalarial medications. The incubation period ranges from seven to thirty days, and human-to-human transmission without a mosquito vector is not possible. Preventative measures often recommended include the use of insect repellents containing DEET, wearing long-sleeved clothing, and, in high-risk areas, taking prophylactic medication.

In the United States, most malaria cases are linked to travel to endemic regions, especially countries in sub-Saharan Africa. The CDC reports that annually about 2,000 to 2,500 cases occur nationally, with Washington State typically reporting 20 to 70 cases each year, all associated with travel. The recent case is notable due to its apparent local transmission, which is exceedingly rare; the last major incident in the U.S occurred in 2023 with ten cases across four states.

The discovery of this local case emphasizes the importance of ongoing mosquito prevention and control efforts even in regions where malaria is not endemic. While the risk to the general public remains low, health authorities are vigilant and continue to monitor the situation closely.

This incident underscores the necessity for awareness about mosquito-borne diseases and reinforces the importance of preventive measures, especially during the warmer months when mosquito activity is highest.

source: https://medicalxpress.com/news/2025-08-malaria-possibly-washington-state-local.html