Renewed Outbreak of Hantavirus Feared

The leaves are changing colors. There’s a brittle chill in the morning air. Footballs are everywhere.

But the arrival of autumn this year heralds concern. Deer mice are seeking hiding places indoors, perhaps bringing with them a virus blamed for as many as 25 deaths in nine states. New Mexico has registered the most fatalities, with 10.

“Cold weather will limit their sources of food and warmth,” said Bill Williams, spokesman for the state health department.

The illness caused by hantavirus is believed to be carried in the airborne particles of dried feces or urine from deer mice.

The disease first broke out in the Four Corners area of New Mexico, Arizona, Utah and Colorado in early June; hantavirus was pinpointed as its cause later in the summer.

Besides New Mexico, other states with confirmed deaths are Arizona, four; Colorado, four; California, two; and Louisiana, Montana, North Dakota, Oregon and Texas, one each, according to an Associated Press survey of state health officials.

So far, 42 people in 12 states have been infected, most of them in the Southwest.

Dr. C. J. Peters, whose lab traced the disease, said it appears that the first documented U.S. case was in North Dakota in August, 1991. But there may have been others.

“A lot of people die of unexplained pulmonary syndromes every year,” said Peters, of the federal Centers for Disease Control and Prevention in Atlanta.

Bob Howard, a CDC spokesman, said health officials now say they are better prepared to deal with the illness if another outbreak should occur this fall. In fact, the CDC began a public information campaign a few weeks ago.

The message has been simple: To minimize the possibility of transmitting the virus to humans, it is critical to reduce food and shelter available to mice.

“By their nature, they’re very opportunistic,” Howard said. “If you eliminate those two things, they will go elsewhere and either predators or the climate will kill them off.”

“It’s not a situation where you need to go on a search-and-destroy mission,” Howard added. “But you want to decrease your chances of coming into contact with mice accidentally.”

The evidence implicating the deer mouse is overwhelming, Howard said. In field trappings near the homes of victims early in the outbreak, more than 95% of captured deer mice tested positive for hantavirus antibodies, he said.

Williams said the virus also has been found in chipmunks, rock squirrels, house mice and pinon mice. But Howard said the evidence points to the deer mouse as the primary source of transmission.

Health officials caution people to stay alert to flu symptoms. “When in doubt, please see your doctor,” Howard said.

Virologists worldwide have seen different strains of hantavirus for decades. The hantavirus is named for the Hantaan River in Korea, where the first strain was discovered. That virus infected about 3,000 American soldiers during the Korean War, killing 190. The virus itself was not identified until more than 20 years later.

Deer mice have been abundant in the Southwest and other parts of the country for centuries. Officials suggest that the hantavirus outbreak this summer was linked to an extraordinarily wet climate over the last year.

Officials say the heavy precipitation over the winter and spring increased the crop of nuts and seeds that deer mice eat. The resulting boom in the rodent population may have contributed to the hantavirus outbreak, some health officials speculate.