Just two years after arriving in the Western Hemisphere, the West Nile virus has traveled all the way to Wisconsin, according to the U.S. Geological Survey's West Nile Virus Wild Bird Surveillance program.
Two juvenile crows in Milwaukee County were found last week to be infected with the mosquito-born virus, which causes serious illnesses in less than 1 percent of humans who become infected by it, according to Dr. Jeff Davis of the Wisconsin Public Health Division Bureau of Communicable Diseases.
Since the birds were juveniles, they would not have migrated to Wisconsin with the disease, Davis said.
'They would have had to acquire their infection from a mosquito in Wisconsin,' Davis said. 'The implication is that it could be in surrounding areas [outside of Milwaukee County].'
Like birds, humans can acquire the virus through mosquito bites. But most people who suffer from the West Nile virus will not even realize they have it, Davis said, because the most frequent symptoms, such as a mild headache or fever, are associated with more common health problems such as a cold or flu. However, in rare instances the virus can cause serious illnesses, including meningitis and encephalitis, a life-threatening disease affecting the brain.
While some states have adopted spraying programs to destroy mosquitoes carrying the disease, Davis said Wisconsin will instead try to educate people about how they can avoid the virus.
'The most prudent mechanism for prevention is personal protection,' he said.
Davis recommended that people avoid outdoor activity between dusk and dawn, wear long sleeves and pants outside, use mosquito repellents, make sure screens fit their windows tightly and refrain from keeping standing water near their homes.
The African virus made its first appearance in the Western Hemisphere in New York in 1999 and has since been carried westward by migratory birds, according to Paul Slota, public relations director for the USGS National Wildlife Health Center in Madison.
Davis said he was surprised by the speed with which the virus has moved across the country.
'To have as much movement of this so far to Georgia, Florida, into Kentucky and west this year into Indianapolis and Detroit and now Milwaukee, certainly would suggest it's moving faster than anticipated,' Davis said. 'We thought at the beginning of this year that we'd see it next year.'
Although the virus is known to have infected more than 80 species of birds, 'crows and other birds in the crow family have been most afflicted to date,' Slota said. 'The bird is actually the target of the virus. The cycle goes mosquito to bird and back to mosquito.'
In order to protect rare and endangered birds, the USGS is testing a vaccine for the virus to be used in birds, Slota said.
