First West Nile Virus Positive Dead Bird Detected in Santa Clara County

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West Nile Virus Season is Off to a Late Start

 SANTA CLARA COUNTY, CALIF. – The Santa Clara County Vector Control District (SCCVCD) has confirmed that one American crow has tested positive for West Nile Virus (WNV) in the South Bay. The bird was found on August 3rd in the city of Santa Clara (ZIP code 95051).

This is the year’s first detection of WNV activity in the county. This low level of WNV activity was also observed at the state level: so far this year, 115 dead birds were confirmed positive to WNV in California, compared to 718 at the same point last year.

“This year, we are having a calm WNV season,” said District Manager Nayer Zahiri. “However, a late start can be followed by a spike of WNV activity.  Residents should keep reporting dead birds and mosquito breeding sources, and taking measures to protect themselves from mosquito bites.”

Dead birds of certain species, such as crows and ravens, are very vulnerable to WNV infection, and act as an early warning system. A bird that tests positive for WNV alerts health officials that the virus is present in an area. Once a positive dead bird is detected, SCCVCD raises its surveillance efforts to confirm if mosquitoes in the same area are infected with the virus.

In response to this discovery, the District will collect adult mosquitos for WNV testing by deploying mosquito traps in the neighborhoods where the dead bird was found. The results of this mosquito testing will be available early next week. The District continues to control mosquitoes in their immature stages through an integrated pest management (IPM) program. The District’s vector control technicians routinely inspect standing water where mosquitoes develop, and treat mosquito breeding sources throughout the county.

Transmitted by mosquito bites, WNV causes mild to severe flu-like symptoms such as fever, headache, body ache, and, in severe cases, significant neurological symptoms or even death. The elderly and those with compromised immune systems are most susceptible. In 2016, California reported 442 human WNV cases, with 19 fatalities. No human cases or WNV positive mosquitoes have been found in Santa Clara County this year.

The SCCVCD asks residents to report fresh carcasses of birds to the California West Nile Virus Hotline at or by phone at 877-WNV-BIRD (877-968-2473).

For more information about mosquito prevention and free assistance on mosquito control, residents can contact the District´s office by calling (408) 918-4770, fill out a service request online at or use the SCCvector app, downloadable at