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Birds are the natural reservoir for West Nile virus. If a
mosquito bites an infected bird and the virus is transmitted to the mosquito, it
may then become a host itself. If the same mosquito then bites a human, it can
pass the disease to the human. Because of this cycle, noticing dead birds could
be the first sign of West Nile Virus in an area.
Wild bird surveillance
Blood samples can be taken from wild birds to see if they are
infected with West Nile and other viruses. During 2001, the Ohio Department
of Health Vector-borne
Disease Program tested 1,848 wild birds. Six were positive for West Nile virus.
No human cases were diagnosed in Ohio. The low percentage of positive birds
suggested that Ohioans were at low risk. What happens in the future is unknown,
but surveillance is the best way to estimate risk
Dead bird surveillance
West Nile virus kills birds, and the most sensitive species in
Ohio are American Crows and blue jays. They almost always die from infection
with West Nile Virus. This is a new virus in the western hemisphere, but some
studies have indicated that a dead crow rate of 1.5 per square mile per week is
a prelude to human cases. Citizens should report dead crows and blue jays to
their local health departments. Clusters of dead crows and blue jays may
indicate increased risk of human disease. This is important to local health
departments. Should they increase their prevention efforts or not? Citizens can
help in this decision by reporting dead crows and blue jays to their local
health department.
Depending on local resources, the local health department may send a person to
inspect the dead bird, determine if it is a American Crow or blue jay, collect
it, and send it in for West Nile virus testing. After two dead birds have been
confirmed as infected with WNV in a calendar year, West Nile virus is considered
to be present and active and there are infected mosquitoes present. No further
birds need be sent for testing.
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