Pierce County woman diagnosed with malaria. Is it first case acquired in WA?
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- An east Pierce County woman was diagnosed with malaria on Aug. 2, health officials say.
- It could be the first known locally acquired case of the disease in Washington.
- The woman, who had not traveled recently, is receiving treatment.
The Tacoma-Pierce County Health Department said Wednesday it is investigating a possible locally acquired case of malaria after a woman who had not traveled recently was diagnosed with the disease on Aug. 2.
If it’s confirmed that the woman was infected with malaria in Washington, it would represent the first known locally acquired case in the state.
“It would be something we haven’t seen in Washington,” Tacoma-Pierce County Health Officer Dr. James Miller told The News Tribune.
The patient, from east Pierce County, is receiving treatment, and health officials are continuing to monitor her status, the health department said in a statement. The department also issued guidance for clinicians, hospitals, and laboratories on Wednesday.
“The risk of getting infected with malaria in Pierce County remains very low,” Miller said in a statement before an interview with The News Tribune. “Malaria is a rare disease overall in the United States — and the vast majority of cases in the United States occur following exposures in countries with ongoing transmission.”
Health officials said they are working with the Washington State Department of Health and the Centers for Disease Control and Prevention to investigate the potential sources of infection.
Malaria, a mosquito-borne disease caused by a parasite, typically causes fever, chills, body and headaches and fatigue. Infected persons can also experience nausea, vomiting, and diarrhea. The disease doesn’t spread directly from one person to another but can be life-threatening if not diagnosed and treated quickly, the health department said. On average, there were nearly seven malaria deaths annually in the U.S. between 2007 and 2022, with fatality rates routinely under 1%, according to the CDC.
While the woman’s case could be unprecedented in Washington, with no previously recorded instance of someone becoming infected while in the state, Miller said in an interview that it’s important to understand there are cases here every year.
“I think there’s always a small risk in Washington, but I don’t think that this event meaningfully changes that risk,” he said.
Washington sees between about 20 to 70 reports of malaria cases annually linked to travel, according to the health department. Across the United States, there are roughly 2,000 to 2,500 travel-related cases each year. In 2023, the United States saw its first locally acquired mosquito-transmitted malaria case in 20 years, and 10 local-transmission cases were ultimately reported across four states over five months, the agency said. The cases were reported in Arkansas, Florida, Maryland and Texas, according to the CDC.
The Anopheles mosquitoes that transmit the disease in the United states can bite someone infected with the disease and then can spread the disease to other people they bite, the health department said. Such opportunities are limited in the United States compared to other countries where malaria is more prevalent, Miller said.
Anytime someone is diagnosed with malaria in Washington, there’s a theoretical possibility that they could later be bitten by a mosquito which could then bite someone else, Miller said. Yet, he also underscored that the locally acquired cases seen in 2023 didn’t lead to ongoing transmission.
As health officials investigate the woman’s source of infection, they are working with the state Department of Health to implement mosquito trapping and testing, the agency said, adding that mosquito populations were fortunately decreasing in Pierce County at this time of year.
Miller told The News Tribune that the investigation, which will consider multiple factors including travel history, might take a few weeks and it’s possible that it won’t reach a conclusion. Ultimately, health officials want the public to be aware and seek treatment if showing symptoms. In most cases, it can take seven to 30 days after infection before symptoms arise, the health department said.
Preventing mosquito bites is the best way to stave off malaria. The health department urged people to use Environmental Protection Agency-registered insect repellant and wear long-sleeved clothing in areas with mosquitoes. People should also use screens on windows and doors and remove or cover sources of standing water such as birdbaths and pools.
Travelers to countries where malaria is more common should also be mindful, the health department said, including by asking a health care provider if medications to prevent malaria are necessary and immediately contacting a doctor if they show malaria symptoms.
This story was originally published August 6, 2025 at 12:09 PM with the headline "Pierce County woman diagnosed with malaria. Is it first case acquired in WA?."
