Hantavirus More Common In The Northwest That Originally Thought

A new study from Washington State University finds the Sin Nombre virus, a hantavirus that can cause a deadly respiratory illness in humans, may be far more common in Northwest rodent populations than previously thought.

Researchers studying rodents in eastern Washington and northern Idaho found nearly 30% showed evidence of past infection, while about 10% were actively carrying the virus.  The virus is primarily found in deer mice and can spread to humans through airborne particles from contaminated droppings, urine, or nesting materials.

The Results Were Surprising

“We were surprised both by how common the virus was locally and by how little data existed for the Northwest,” said Stephanie Seifert, the study’s corresponding author and principal investigator of the Molecular Ecology of Zoonotic and Animal Pathogens lab in the College of Veterinary Medicine’s Paul G. Allen School for Global Health. “We’re really just beginning to understand how widespread and complex this virus is in rodent populations here.” 

Research Focused On The Palouse Region

The study also uncovered the first full genome sequences of Northwest strains, helping scientists better track how the virus evolves.  Researchers say human infections remain rare, but some cases may be going undetected.

Activities that disturb rodent droppings or nests can increase the risk of exposure by sending virus particles into the air. Sweeping or using equipment like leaf blowers in enclosed areas can be particularly hazardous. Instead, health officials recommend ventilating spaces and using wet-cleaning methods to reduce the risk of inhalation.

Field work for the study was done in the summer of 2023 when researchers trapped rodents across farms and natural areas in Whitman County, Washington, and Latah and Benewah counties in Idaho. In total, samples were collected from 189 animals, including deer mice, voles and chipmunks.

People May Be Exposed More Often Than They Realize

Once in the lab, the researchers identified active infections and antibodies, indicating a past infection, in both deer mice and voles, suggesting the virus may move between species.

The researchers also used the samples to produce the first full genome sequences of SNV strains from the Northwest. The sequences revealed high levels of genetic diversity and evidence of viral reassortment, or mixing of genetic material. The information can help public health officials and scientists track how the virus evolves in the future, in addition to assisting in identifying sources of infection and improving surveillance and testing.

”People may be exposed more often than we realize, but severe cases are more likely to be tested for hantavirus,” said Pilar Fernandez, a co-author on the study and a disease ecologist in the Allen School whose research focuses on the eco-epidemiology of zoonotic diseases. “Understanding that gap – how exposure translates into disease – is the next big step.” 

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