Hantavirus found in over 30 small mammal species in New Mexico

Hantavirus isn’t just in deer mice, according to a new peer-reviewed study from the University of New Mexico, which found the virus in a quarter of more than 1,400 small mammals tested across the state.

Hantavirus is a rare but often serious rodent-borne illness, which first reared its head in the United States in the Four Corners region in 1993. From 1993 through 2022, New Mexico had 122 human cases and 52 deaths — more than anywhere else in the country, according to the Centers for Disease Control and Prevention.

The illness recently made international headlines for causing the death of Betsy Arakawa, a Santa Fe businesswoman and renowned actor Gene Hackman’s wife. The couple’s remains were found Feb. 26 in their Santa Fe home.

“The hantavirus research — because it’s really close to home — it is something that my lab focuses a lot of attention on,” said Steven Bradfute, one of the paper’s authors and an associate professor at the Center for Global Health within UNM’s Department of Internal Medicine. A mouse living in a cactus in Bradfute’s front yard was one of the rodents that tested positive for hantavirus.

Deer mice were identified in the 1990s as the primary carrier of hantavirus in New Mexico. The most common strain of hantavirus in the U.S. can cause hantavirus pulmonary syndrome, which kills approximately 35% of people who contract it. People often catch hantavirus from breathing in aerosolized rodent feces or being bitten or scratched by an infected rodent. The virus cannot be passed from person to person.

Bradfute was curious why deer mice can be found all over the state, but people sick from hantavirus aren’t. So researchers began trapping rodents in areas where there is hantavirus infection and areas where there isn’t, like the southeast region. Research in the 1990s identified hantavirus genes in other rodents, and the CDC warns deer mice, rice rats, cotton rats and white-footed mice can all spread it.

But the new study shows that other rodent species, including ground squirrels, chipmunks, gophers, rats and house mice, can grow the virus and shed it — suggesting they could be capable of spreading the illness to people.

“Live virus can be isolated from many rodent species, so it’s not just spillover, where they just kind of get infected and it goes away. They can actually shed live virus,” Bradfute said.

The study complicates Bradfute’s original curiosity: if hantavirus can be found in rodents all over the state, why are most of the human cases concentrated in McKinley, San Juan and Taos counties? Researchers have some ideas for future study:

• It’s possible hantavirus cases in people are being underreported. Researchers are looking to see if people who live in places with no known infections have antibodies against the virus.
• Conditions in northwestern New Mexico, like humidity or temperature, might make it easier for the virus to get aerosolized, Bradfute said, or rodents in the Four Corners region may have higher concentrations of the virus.
• The virus itself could be different in different parts of the state, with a version better at causing disease circulating in the northwest region. To study that possibility, researchers are sequencing the virus samples, a tricky process.

“We found Sin Nombre virus in the rodents in Quay County. … Then this last year, unfortunately, there was the first ever hantavirus case in Quay County, and it was fatal. So that really woke us up to, OK, we really need to be looking at these other areas, because we know the virus is there,” Bradfute said.

UNM Ph.D. student Samuel Goodfellow and research scientist Robert Nofchissey were also authors on the study, published in PLOS Pathogens in January.