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West Nile Virus moves to Iowa

Dead crow in September first sign

By Kathryn Ratliff-Howe Iowa City Press-Citizen

West Nile Virus, on a westward journey in the United States since its arrival in 1999, will be present in Iowa in full force this summer, state public health experts say.

Currier "As much as it moved this past year, barring some weather catastrophe like a 300-year drought and no mosquitoes anywhere, we will see this extend throughout all counties in 2002," said Russell Currier, environmental epidemiologist with the Iowa Department of Public Health. "We will have West Nile from now through the end of time."

In September, the state health department reported that a dead crow found in Scott County tested positive for West Nile Virus, marking its presence in Iowa for the first time. The crow is the only evidence of West Nile in Iowa so far, however, experts believe it is probably present in other counties.

West Nile Virus can cause encephalitis, which is inflammation of the brain, and is transmitted by mosquitoes. It is deadly to birds and other animals, but poses only a small health risk to humans. No human cases have been reported in Iowa.

Currier predicts that by the time the virus establishes itself in Iowa this year, two to four human cases will be reported each year after, with one death per decade.

West Nile virus symptoms

• The chances you will become severely ill from a mosquito bite are small. • Most people infected with West Nile Virus have no symptoms. A small percentage develops mild symptoms that include fever, headache, body aches, skin rash and swollen lymph glands. • Less than 1 percent of infected people develop more severe illness that includes meningitis or encephalitis. Symptoms include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness and paralysis. • Of the few people who develop encephalitis, a small proportion die but this is estimated to occur in less than 1 out of 1,000 infections. Birds, on the other hand, are in trouble.

West Nile Virus is transmitted to humans through mosquito bites. Mosquitoes become infected when they feed on infected birds that have high levels of the virus in their blood. Infected mosquitoes can then transmit the virus when they feed on humans or other animals.

Mary Gilchrist, director of the University of Iowa Hygienic Lab, said there will be a contiguous spread of West Nile from Scott County. The virus' prevalence will depend on how warm and moist it is for mosquitoes, she said.

"We know we have a very strong probability that it will have a major effect on our bird population," Gilchrist said. "We will see a lot of dead birds."

Gilchrist said her lab will be soliciting birds - primarily crows and blue jays - from Iowa counties not yet known to be affected by West Nile so the state can track the virus' presence and movement.

The lab's Web site also will provide information on what counties have detected West Nile. June will be the first month of concern, Gilchrist said.

Not person to person

West Nile Virus is not transmitted from person to person and there is no evidence that a person can get infected by handling live or dead bird infected with the virus. Most infected humans have no symptoms. A small proportion develops mild flu-like symptoms. Less than 1 percent develop more severe illness that includes meningitis or encephalitis, which is inflammation of the brain. Out of those who develop encephalitis, a small proportion die.

Reducing risk

People can reduce contact with mosquitoes and therefore their risk of West Nile infection by:

• Wearing clothing that covers the skin, such as long-sleeved shirts and pants, when outdoors. • Applying effective insect repellent to clothing and exposed skin. An effective repellent will contain 35 percent DEET (diethyl-meta-toluamide). • Curbing outside activity during the hours that mosquitoes are feeding, which includes dawn and dusk. • Screens should be applied to doors and windows and regularly maintained to keep mosquitos from entering the home. • Be sure to clean gutters, birdbaths and get rid of old tires, all of which can collect water and become natural gathering grounds for mosquitoes. People 65 and older and the very young are most vulnerable to developing severe illness from West Nile infection. Most people who die are elderly. Iowa is a state at particular risk with the highest percentage of people 85 and older in the nation.

Cases occur during mosquito season in the late summer and early fall.

There is no specific treatment for West Nile infection or vaccine to prevent it. Medical care should be sought immediately for people who have symptoms suggesting severe illness.

Since the 1930s, West Nile Virus has been found in humans, birds and other vertebrates in Africa, Eastern Europe, West Asia and the Middle East. Scientists believe the virus first made its appearance in the eastern United States in the summer of 1999.

U.S. origins

It is not known exactly where the U.S. virus originated, but it is most closely related to strains found in the Middle East. In 1999 and 2000, outbreaks of West Nile encephalitis and other illnesses were reported in people living in the New York City area. In these two years, 83 human cases of West Nile were reported and nine people died.

In 2001, the first cases of West Nile encephalitis outside the New York City area occurred when two cases were reported from a rural Florida county in July and August. The virus has continued to spread toward the west. It has now been documented in more than 20 states.

The continued expansion of West Nile Virus in the United States suggests that it is permanently established in the Western Hemisphere. Iowa borders Illinois and Wisconsin, both of which have reported the presence of West Nile Virus. Currier said he thinks the virus will extend to the Missouri River and beyond before the end of the 2002 mosquito season.

Iowa's mosquito surveillance program was upgraded in 2000 to include screening for West Nile. The program involves the trapping and testing of mosquitoes, testing bird flocks around the state and testing of dead birds sent in from across Iowa.

Ralph Wilmoth, director of the Johnson County Public Health Department, said the department is adding information about West Nile to its Web site. Anyone intending to report a dead bird should first contact the health department for submission to the UI Hygienic Lab for testing, he said.

Gilchrist said the lab also will be tracking a virus that first came to Iowa last fall called eastern equine encephalitis, also transmitted by mosquitoes. This is a more serious pathogen that can affect the brain permanently and can impact a wider age range, she said.

The lab, with the help of Iowa State University and the state health department, tracks encephalitis viruses in birds and mosquitoes every year. Eastern equine encephalitis will be added to the watch list.

Background and data provided by the U.S. Centers for Disease Control and the U.S. Geologic Survey.

-- Anonymous, January 18, 2002