Washington state officials have revealed that a local woman has been diagnosed with malaria, which, if confirmed, would mark the first known case of the disease being acquired in the state.

The woman was diagnosed with malaria, a mosquito-borne illness caused by a parasite, on August 2, according to the officials. State and federal public health agencies are working to confirm the source of the infection, according to a statement published on Wednesday.

Officials believe that the infection may have been transmitted by a mosquito that bit someone else who already had a travel-associated case of malaria. The woman is currently receiving treatment and is being closely monitored. Symptoms of the disease include fever, chills, body aches, fatigue, vomiting, and diarrhea. It can take up to 30 days for an infected person to start showing symptoms.

Cases of malaria in the U.S. are typically linked to travel—mainly to visitors with ties to sub-Saharan African countries—and the disease is not considered endemic to the U.S. In fact, the U.S. effectively eradicated malaria in the 1950s thanks to aggressive control measures, including pesticides and improved drainage. But the Anopheles mosquito which transmits malaria lives all over the country: If they bite someone infected with the disease, the bugs could feasibly transmit the parasite that causes malaria to other people in the area.

Between 20-70 cases of malaria are recorded in Washington each year and there are typically around 2,000 cases annually across the U.S., according to official estimates. While many are linked to travel, there has been a recent uptick in locally-acquired infections.

In 2023, the U.S. experienced its first locally acquired malaria case in 20 years. And between May and October of that year, 10 such cases were reported across Florida, Texas, Maryland, and Arkansas.

Climate change may be driving the incidence of local malaria infections up: The parasite that causes malaria needs warm temperatures to thrive, and research suggests more cases of the disease could arise in previously malaria-free areas as the planet warms.

The U.S. has historically been the top donor nation to global efforts to combat malaria, according to health nonprofit KFF. But those initiatives took a hit when the Trump administration slashed the country’s foreign aid programs earlier this year, including most of the work of the President’s Malaria Initiative—a USAID program launched in 2005 focused on reducing malaria in countries where the disease is endemic.

As part of the investigation in Washington, officials are working with the U.S. Department of Health to trap and test mosquitoes. Local authorities have stressed that people in the area of the state where the woman was infected remain at very low risk of contracting malaria.

“The risk of getting infected with malaria in Pierce County remains very low,” James Miller, health officer for Tacoma-Pierce County, said in a statement. “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.”