Hantavirus Threat Found in County : Health: A strain of the virus that has killed 42 people is found in mice trapped at Crystal Cove State Park. Health officials urge hikers to take precautions.

Researchers in Orange County and New Mexico said Thursday they have identified a new and potentially deadly strain of the hantavirus in harvest mice trapped in Crystal Cove State Park.

The hantavirus previously found in deer mice killed 42 people in 18 states, mostly in the Four Corners area of the Southwest. Among the fatalities were two California cases, but there were none reported in Orange County.

“There’s no way to tell from the data we have now whether (the new strain) has any disease-causing ability, but because it is close to the Four Corners strain, we have to assume that it may have that capability,” said James P. Webb, Jr., ecologist with the Orange County Vector Control District.

Officials in New Mexico, where at least one harvest mouse with the strain was identified, announced its discovery Thursday.

Webb said that no people have been infected, and Orange County health officials have no plans to bar visitors to Crystal Cove.

“We’re recommending that this is another precaution in going into wild areas, along with poison oak, mountain lions, rattlesnakes and coyotes,” Webb said. “Stay on the trails there, and you’re probably not going to have any problems.”

Hikers who leave the trail “shouldn’t be kicking up a lot of dust, or digging holes or trenches. Make sure to camp in an area that’s free of rodents or rodent droppings,” he said.

Routine testing of rodents in recent months turned up five infected harvest mice--four at Crystal Cove and one in South County, near the TRW testing facility, according to Webb.

*

The harvest mice had been collected earlier this year and sent to New Mexico, where they were analyzed by Brian Hjelle, assistant professor of pathology at the University of New Mexico School of Medicine in Albuquerque.

“They determined that initially we have another species of mouse, a harvest mouse, carrying a related strain of hantavirus related to the Four Corners virus,” Webb said.

“Subsequently, we sent in another sample from harvest mice” from the Crystal Cove area, Webb said, taken after the Laguna fire in January. “Out of that came four more positives.”

There are distinct differences between the different harvest mice and deer mice, which were responsible for the deaths.

The harvest mouse, Webb said, “tends not to go into buildings. It is found in more grassland areas, and builds its nest on the ground, it does not tunnel under the ground.”

In the initial outbreak, people became infected with the hantavirus by inhaling airborne particles of urine or saliva of infected deer mice. Early symptoms of the illness mirror the flu.

The disease progresses rapidly, causing breathing difficulties and filling the lungs with fluid. Hantavirus is fatal about 60% of the time.

The Associated Press contributed to this report.