West Nile Virus Information
West Nile Virus (WNV) is transmitted by the bite of an infected mosquito. It is widespread in Africa, southern Europe, and western Asia. WNV first appeared in the United States in 1999 in the greater New York City area. It has caused illness and mortality in humans, wildlife and domestic animals, especially birds and horses. In humans, West Nile Virus causes an influenza-like illness that may lead to aseptic meningitis, encephalitis, and death, especially in persons over 50 years of age. Learning about symptoms of WNV is important because it affects not only people, but also wildlife and some domestic animals, primarily horses. If you find a dead bird, please contact your local health department.
In August 2002, a number of great horned owls and red-tailed hawks were observed across Ohio on the ground, alive, but not responsive to danger. West Nile Virus was presumed to be the cause of these birds’ illness, and led to the death of hundred of owls and hawks throughout Ohio. Test results issued by the National Wildlife Health Laboratory (NWHL) in Madison, Wisconsin indicated that these birds likely were affected by WNV. While there is no vaccination or treatment for birds with WNV, hundreds of birds were cared for by licensed wildlife rehabilitators across the state.
It is not known if raptors in Ohio will continue to experience a similar impact by WNV. Persons who see a live raptor which appears thin, weak, unable to fly or stand, is easily approachable, and is not responsive to danger should contact a licensed Wildlife Rehabilitator for assistance.
According to the NWHL, since 1999, WNV has been detected in over 160 wild and captive bird species. This is based on reports from public health, wildlife, and veterinary diagnostic laboratories across the United States.
While birds are the natural host and reservoir of WNV, other animals, including several mammals and a reptile, are susceptible to WNV infection. There is currently no evidence that animals other than birds develop a high enough virus load to transmit the infection to an uninfected mosquito.
Unfortunately, at this time, we do not know if WNV is having a serious overall impact on bird populations. While we do know that the virus kills some species of birds, it is difficult to document the effect WNV has had on wild bird populations. Based on 2002 Christmas Bird Counts, Breeding Bird Surveys, and reports from bird enthusiasts, we know there have been declines in observations of many local bird populations. However, we do not know if this is a true decline or if the decline can be positively attributed to WNV. While we may observe local declines in some bird species, avian populations are resilient and strong birds will sustain the species.
To learn more about WNV, visit the following websites:
To learn more about the Ohio Wildlife Rehabilitators’ Association visit their website at: