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Researchers from Washington State University have uncovered unexpectedly high levels of hantavirus among rodents in the Pacific Northwest, raising concerns about increased exposure risks for nearby agricultural communities. The study focused on the Palouse region, which spans parts of eastern Washington and north-central Idaho.
The team, based in WSU’s College of Veterinary Medicine, tested 189 rodents-including deer mice, voles, and chipmunks-collected during the summer of 2023 from farms and forested areas. Results revealed that nearly 30% of these rodents had prior exposure to Sin Nombre virus (SNV), the hantavirus strain most closely linked to hantavirus pulmonary syndrome (HPS), while about 10% were actively infected.
While deer mice have traditionally been recognized as the primary carriers of SNV, infections were found across multiple rodent species, suggesting that the virus may be more widespread in the region than previously believed.
Published in the Centers for Disease Control and Prevention’s peer-reviewed journal Emerging Infectious Diseases, the study highlights a significant gap in data for the Pacific Northwest. “We were surprised both by how common the virus was locally and by how little data existed for the Northwest,” said Stephanie Seifert, lead investigator and principal researcher at WSU’s Paul G.
Allen School for Global Health. “We’re just beginning to understand how widespread and complex this virus is in rodent populations here.”
It is important to note that the Sin Nombre virus typically spreads to humans through inhalation of aerosolized rodent urine, droppings, or saliva and is not known to transmit from person to person. This distinguishes it from the Andes virus, recently linked to a hantavirus outbreak on a cruise ship, which can spread through close human contact.
Dr. Sonja Bartolome, a pulmonary specialist at UT Southwestern Medical Center, emphasized the rarity of hantavirus cases in the U.S., with fewer than 900 cases reported nationally since 1993, primarily concentrated west of the Mississippi River in states like Colorado, New Mexico, and Arizona. She added that studies comparing viral genetics across regions and species are vital to understanding the virus’s movement and transmission.
The study’s authors acknowledge limitations, including its focus solely on rodents without direct assessment of human transmission risk, sampling restricted to the Palouse region, and data collected during a single season. Nevertheless, the findings underscore the need for expanded monitoring of hantavirus in the Pacific Northwest, particularly in agricultural zones.
Researchers advise that residents and farmers in rural areas take precautions to minimize contact with rodents and their excreta. Longer-term studies could provide insight into how environmental factors and seasonal changes impact hantavirus prevalence.
“People may be exposed more often than we realize, but severe cases are more likely to be diagnosed,” noted co-author Pilar Fernandez, a disease ecologist involved in the study. “Understanding how exposure leads to disease is the next critical step.”