As passengers from the hantavirus-stricken cruise ship are being monitored, unusually high levels of the virus have been detected in rodents in the US.

Researchers found that a significant portion of rodent populations in the Pacific Northwest — specifically the Palouse region of Washington and Idaho — were carrying the Sin Nombre virus (SNV).

The findings indicate that not only is the virus more widespread than initially realized, but it could also increase exposure risk in surrounding agricultural communities.

Published in the Emerging Infectious Diseases journal, researchers from Washington State University’s College of Veterinary Medicine collected samples from 189 deer mice, voles and chipmunks in summer 2023.

Nearly 30% of rodents from both farm and forest settings showed evidence of past infection with the virus and 10% had active infections.

SNV is the strain most strongly linked to hantavirus pulmonary syndrome (HPS), the more common form in the US.

The condition can cause flu-like symptoms that quickly progress to breathing difficulties and significantly damage lung tissue, leading to fluid accumulation in the lungs and serious lung and heart problems.

“We were surprised both by how common the virus was locally and by how little data existed for the Northwest,” study author Stephanie Seifert said in a press release.

“We’re really just beginning to understand how widespread and complex this virus is in rodent populations here.”

Unlike the Andes virus, the rare and deadly strain linked to the MV Hondius cruise ship, the Sin Nombre virus is not known to spread person-to-person.

Instead, it typically transfers to humans through inhalation of aerosolized rodent urine, droppings or saliva.

SNV has remained rare since it was first identified back in 1993 in the Four Corners region of the US, with 864 cases reported between 1993 and 2022. A total of 109 of those cases occurred in Idaho, Oregon and Washington.

This research helps to better understand how the virus spreads throughout a region and offers precautions, according to experts.

“Because humans most commonly contract hantavirus through exposure to aerosolized rodent urine or droppings, precautions remain essential when cleaning areas with evidence of rodent activity,” Dr. Sonja Bartolome, an expert in pulmonary and critical care at UT Southwestern Medical Center in Dallas who wasn’t involved in the study, told Fox Digital News.

Sweeping or using a leaf blower can disturb rodent droppings and increase the risk of exposure by sending virus particles into the air.

Health officials instead recommend alternative cleaning methods, like wet-cleaning methods, to reduce potential inhalation.

The findings also suggest the need for expanded hantavirus monitoring in agricultural areas of the Pacific Northwest, as well as how often people are exposed and how human behavior influences risk.