The appearance of the West Nile virus in northern Florida is troubling health officials, who are disturbed by its leap from the expected migration path.
The virus first appeared in North America two years ago in New York and was expected to spread state by state. It was discovered this month in a dead crow in the Florida Panhandle, disrupting the expected pattern, according to the Centers for Disease Control and Prevention in Atlanta.
On Friday, the Florida Department of Health said preliminary tests of three additional crows found in northern Florida showed evidence of West Nile virus. Experts at the CDC say the virus, carried in birds and mosquitoes, has spread south faster than expected or has reached Florida by another route.
"The finding in Florida is the first time we have identified the virus in a noncontiguous area," said Dr. David Ostroff, the coordinator for the West Nile virus at the centers, "and the first time its spread has been identified during the time of year that is not the tail-end of when birds are migrating. In June and July in northern Florida there is not much bird migration going on."
Five other states that previously reported positive tests for West Nile virus have discovered new cases this year, the CDC said. They are New York, New Jersey, Connecticut, Maryland and Rhode Island. With the addition of Florida, 12 states and the nation's capital have now confirmed cases of the virus, the centers said.
The other states are New Hampshire, North Carolina, South Carolina, Pennsylvania, Delaware and Virginia. Last year, the virus spread virtually county-by-county from one state to the next, down the East Coast, Ostroff said.
Experts say it is too early in the mosquito season to estimate how far the virus will spread this year or how many people are likely to become infected.
Florida health officials say they have been bracing for the arrival of the virus, given its southern movement, and have now stepped up efforts to control its spread and to tell people about its potential dangers, said Dr. Steven Wiersma, an epidemiologist with the Florida Department of Health.
The virus, which is native to West Africa, mostly infects birds and mosquitoes but can also be contracted by animals and people through mosquito bites. Most people who get it do not become ill or experience only mild flulike symptoms. But it can cause encephalitis and it can be fatal, particularly for the elderly and people with weak immune systems.