A Washington State University research team has found that a significant share of rodents tested across the Palouse region carried signs of Sin Nombre virus, the pathogen responsible for hantavirus pulmonary syndrome in humans — and the findings suggest the virus may be far more common in the Pacific Northwest than previously understood.
Field sampling took place during the summer of 2023 across farms and natural areas in Whitman County, Washington, and Latah and Benewah counties in Idaho. Researchers collected samples from 189 animals, including deer mice, voles, and chipmunks. Results showed that roughly 30% of tested animals showed evidence of past infection, while approximately 10% carried active infections — meaning they could potentially transmit the virus.
The study was published in the CDC’s Emerging Infectious Diseases journal.
What the Findings Mean for Palouse Residents
Sin Nombre virus can cause hantavirus pulmonary syndrome, a serious and sometimes fatal respiratory illness. Human infection typically occurs when a person inhales airborne particles from rodent droppings, urine, or nesting material — a risk that increases when disturbing enclosed spaces such as barns, sheds, or outbuildings where rodents have been active.
Health officials recommend thoroughly ventilating enclosed areas before entering and using wet-cleaning methods to remove rodent waste. Dry sweeping or using blowers should be avoided, as those methods can scatter infectious particles into the air — a practical concern for Latah County residents who work in agricultural settings or maintain older rural structures.
Corresponding study author Stephanie Seifert noted the results were unexpected. “We were surprised both by how common the virus was locally and by how little data existed for the Northwest,” she said in remarks tied to the study’s release.
New Genomic Data Could Improve Future Surveillance
Beyond the infection rates, researchers produced the first complete genome sequences of Sin Nombre virus strains collected from the Northwest. That data could strengthen surveillance programs and help scientists track how the virus evolves over time — a gap that has limited public health preparedness in the region.
Active infections were confirmed in both deer mice and voles, and researchers said that finding raises the possibility the virus may spread between species, complicating efforts to contain or monitor it in wild rodent populations.
Despite the prevalence of the virus in local rodents, documented human cases remain rare. Study co-author Pilar Fernandez suggested that gap may reflect underreporting rather than a true absence of human exposure. “Severe cases are more likely to be tested for hantavirus,” she noted, adding that understanding how often exposure translates into serious illness is a key next step for the research team.
For Latah County residents — particularly those working in agriculture, hunting, or maintaining rural properties — the findings serve as a timely reminder to take rodent exposure seriously. Sealing entry points, avoiding contact with rodent nesting material, and following proper cleanup protocols can significantly reduce risk.
For other public safety developments in the region, see the Latah County Sheriff’s Office active scene investigation in Juliaetta. Statewide health and public safety coverage is available at Idaho News.
What Comes Next
The WSU research team indicated future work will focus on better understanding the relationship between rodent exposure rates and actual human illness — a critical step toward improving public health guidance for rural communities across northern Idaho and eastern Washington.