The first case of the West Nile virus in Story County was confirmed Tuesday, but officials say the public has little need for concern.

The virus, which can be fatal, is carried by mosquitoes and can be transmitted to birds, animals and humans, said Wayne Rowley, professor of entomology. The virus is not transmitted from contact with infected birds, he said.

Rowley said the virus, which originated in Africa, was first discovered in the United States in 1999.

The first documented case of the virus in Iowa was found in Scott County last fall, and seven Iowa counties have reported cases thus far.

“The first case of West Nile virus in the U.S. showed up in 1999 in New York,” Rowley said. “In three years, [the virus] has spread to as far west as the Rockies.”

According to information distributed by the Iowa Department of Public Health, the West Nile virus interferes with normal central nervous system functioning and causes encephalitis, an inflammation of brain tissue.

Thomas Gahan, public health microbiologist at the University of Iowa, said the general public is at risk for contracting the West Nile virus through mosquito bites, but most cases of the virus are mild.

“Most people who contract the virus are asymptomatic – they may develop a fever or headache,” Gahan said. “Severe cases are rare – fewer than 1 percent of total cases develop pretty significant encephalitis.”

He said the severe cases of encephalitis usually develop in the very old and very young, as well as in those with compromised immune systems.

“From 1999 through 2002, there have been 149 serious cases reported in the U.S., with 18 fatalities,” Gahan said. “In terms of a three-year history, it’s fairly low – it’s really low, actually.”

There have been no reported human cases of the West Nile virus in Iowa, he said.

Rowley said the West Nile virus is “amplified” in bird populations, and the virus is detected in dead birds reported by members of the general public.

“There’s a virus cycle between mosquitoes and wild birds,” he said. “Blue jays and crows are most likely to get sick and die from the virus.”

City of Ames Sanitarian Kevin Anderson said the virus was found after a concerned citizen contacted Ames Animal Control.

“We had a dead crow that was called to the attention of animal control officials last week,” Anderson said.

The crow was then shipped to the state hygienic lab in Iowa City for testing, as directed by state of Iowa regulations, he said.

“The state of Iowa has been anticipating the spread of the West Nile virus,” Anderson said. “Public health officials were given materials and instructions on how to handle dead birds suspected of having the virus.”

Gahan said the state hygienic lab has received a number of dead birds this summer from Iowa communities.

“We’ve probably had at least 50 birds submitted, and eight tested positive,” he said.

Gahan said once the lab receives an infected bird from county officials, the results are reported to the respective county’s public health department.

“Once we have confirmed one case of infection, we assume the virus is present in the entire county,” he said. “After that, we do not accept any more birds from the county.”

Rowley said the dry weather this summer has likely affected the spread of the West Nile virus by limiting the breeding and growth of mosquitoes, which thrive in wet weather. However, there are steps residents can take to eliminate mosquito breeding sites, he said.

“The mosquitoes that transmit the virus from bird to bird breed in water-holding containers,” Rowley said. “People should eliminate sources of standing water – such as wading pools, unused birdbaths and buckets – that might be in their own backyards.”

Avoiding contact with mosquitoes is the best defense against the West Nile virus, Gahan said. By staying indoors when mosquitoes are active, wearing insect repellent with DEET and wearing long-sleeved shirts and long pants when outdoors, people can reduce their chance of being bitten, he said.

“This is nothing to lose sleep over,” Gahan said. “People should just be aware West Nile is here and there are precautions that can be taken against it.”