A shocking number of Pacific Northwest rodents may carry hantavirus, study finds

PACIFIC NORTH WEST (KTVZ) -- A surprising number of rodents in the Pacific Northwest are carrying hantavirus, raising concerns about potential human exposure in parts of the region, including eastern Washington.

A recent study, reported by Scientific American, found that about 10 percent of rodents tested had active infections of the Sin Nombre virus, a type of hantavirus. Nearly 30 percent showed evidence of prior exposure.

Researchers collected samples from rodents across eastern Washington and western Idaho, including mice, voles and chipmunks. The findings suggest the virus may be more widespread in local rodent populations than previously understood.

According to the Centers for Disease Control and Prevention (CDC), the Sin Nombre virus spreads to humans through contact with rodent droppings or urine, not from person to person. While human infections remain rare, the virus can be severe, with a mortality rate as high as 50 percent.

Of the 864 hantavirus cases reported in the United States between 1993 and 2022, 109 occurred in Washington, Oregon and Idaho, pointing to a disproportionate number of cases in the Pacific Northwest.

Researchers say environmental factors, including wetter and warmer winters, may be contributing to larger rodent populations and increased risk of exposure.

The study comes as hantavirus has recently made headlines. On May 7th, KTVZ News reported that, in early April, a retired oncologist from Bend who volunteered to treat passengers during an outbreak aboard a cruise ship initially tested positive for the virus. Follow-up testing later confirmed the result was a false positive.

Researchers say more study is needed to better understand how widespread the virus is in the region and how risks to humans may be changing.