The Heat Is Online

CDC Officials Cite Rise in Climate-Driven Hantavirus Cases

Reuters News Service, June 28, 1999

ATLANTA - U.S. cases of an often-fatal respiratory illness first recognised in 1993 rose sharply this year because weather conditions allowed the mice that most often spread the disease to flourish, health officials said today.

The federal Centers for Disease Control and Prevention (CDC) said that there were 18 suspected or confirmed cases of hantavirus pulmonary syndrome during the first five months of this year, compared with an average of two cases during the same five-month period in 1995 through 1998.

James Mills, chief of a medical ecology unit in the National Centre for Infectious Diseases, said the cases reported this year "are more cases than we have seen for this period in any year since we've been monitoring the disease."

Of the 217 people who have developed the disease since 1993 in 30 states, 43 percent have died, the CDC said. The rodent-borne illness first attracted attention when it killed 11 people in northwestern New Mexico in 1993.

The deadly lung infection is caused by a hantavirus carried by rodents and passed to humans through infected rodent urine, saliva or droppings. A primary symptom is difficulty in breathing caused by fluid buildup in the lungs. It quickly progresses to an inability to breathe.

Mills said rainy weather followed by a mild winter contributed to an increase in the population of deer mice, the primary carrier of the virus that causes the illness.

"In 1997, there was an El Nino event which brought unusual quantities of rainfall to the usually dry southwestern United States. This resulted in increased vegetation greenness, improved habitat and increased food quality for the deer mouse population," Mills said.

"Populations reached very high densities by the spring of 1998 in response to this. What has happened in 1999 is that we had a relatively benign winter. A high percentage of the population survived over the winter," he said.

Mills said increased population densities have led to more transmission of the virus between deer mice "which results in increased chances of humans coming into contact with infected mice." The sooner someone with the lung infection seeks medical treatment, the better the chance of recovery, he said.

"The probability of surviving this disease is proportional to how quickly one is hospitalized and enters into intensive care, which may involve supplemental oxygen," Mills said.

Confirmed cases of hantavirus pulmonary syndrome have been reported this year in Colorado, New Mexico, New York and Washington. Suspected cases with preliminary evidence of the illness have been reported in Arizona, California, Idaho, Iowa, Montana, New Mexico and Washington, the CDC said.
Reuters News Service