NEW - Movie Maps!
WNV-positive birds in
2009 through Aug18
(.wmv file, 1.2 MB)
WNV-positive birds in
(.wmv file, 1.7 MB)
West Nile Virus (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.
To report a dead
bird in Los Angeles County, click
read more about WNV in humans, click
Weekly WNV Map
Starting 10.8 and continuing
until approximately March 2010, the state's West
Nile Virus testing program (which conducts most
WNV tests for LA County Public Health) discontinued testing
dead birds for the winter. However, LA County Public
Health is able to
test individual CROWS
for WNV during this time. LA Public County Health
can also conduct tests in cases where there is a die-off
of three of more birds.
As always, thanks to Los Angeles County residents,
Animal Control Agencies, and vector Control Agencies for
you assistance with WNV surveillance.
The number of birds tested varies by month and by year.
By monitoring the percentage of tested birds that were
positive, we have a way of comparing years.
2003: West Nile Virus first arrived in Los
Angeles County late in the year (not shown)
2004: This was one of the most severe WNV
seasons. The percentage of WNV-positive birds increased
dramatically in April, and peaked In August, with 88% of
dead birds collected being WNV-positive.
2005, 2006, 2007: These three years were much
milder in terms of WNV than 2004 and settled into a
consist pattern. The season appeared to start in June
each year, and peaked in August with 55% of tested birds
2008: A dramatic increase in WNV was seen, with
the season beginning in May and peaking in August with
77% of dead birds testing positive. The reasons for this
resurgence of WNV are not known. One theory is that an
increase in neglected swimming pools, caused by the
financial crisis, may have been a large contributor.
2009: The WNV season was milder than in 2008.