Overall 2011 was a very
active year for West Nile Virus (WNV). WNV was
detected in 226 dead birds (200 crows, 6 House finches, 5 House sparrows, 4 Cooper's hawks,
4 Western Scrub Jays,
2 California Towhees, and a single bird each of: raven,
Great Horned Owl,
Oak Titmouse, Mourning Dove
and Red-shouldered Hawk). There were also 15 dead
squirrels that tested positive.
The number of local human
cases detected was 63.
A 4-year old horse in the San Gabriel Valley
also contracted West Nile Virus in August.
The horse had not been vaccinated.
A significant amount of these
WNV-infected birds were found in the
eastern section of the county. The city of
Cerritos had more WNV-positive dead birds
than other cities, with 33 out of the 225 being discovered there. On the map to the
right, many of the WNV-positive dead birds in Cerritos
appear as one red star because they were found
together. See second map below for a close-up of this area. All but one of the WNV-positive dead birds were
discovered since the beginning of June.
WNV is transmitted to humans, horses, and
birds by the bites of infected mosquitoes. Testing dead
wild birds for WNV
provides a way
tracking the virus in our environment. Veterinary Public
Health works with the California Department of Public
Health and local mosquito control agencies in conducting
WNV surveillance in Los Angeles County.
Cases of WNV infection in birds and people tend to be highest in the late summer, but may
be happen at other times.
As always, many thanks to Los Angeles County residents,
Animal Control Agencies, wildlife rehabilitators, and Vector Control Agencies for
all of your work on WNV surveillance!
To report a dead
bird or tree squirrel in Los Angeles County, click
read more about WNV in humans, click