The District’s West Nile virus surveillance program reports
several types of positive West Nile virus results, including dead
birds, mosquito samples (“pools”), sentinel chickens, and human
cases.
For more information about the District’s West Nile virus and
mosquito population surveillance, visit the Mosquito Surveillance page.
As of October 31, 2020, there have been 204 dead birds reported
in San Mateo County. Of those, 62 have been suitable for testing
and one has tested positive for West Nile virus (WNV). The WNV
positive bird was an American crow collected from South San
Francisco in September. This has been the only detection of WNV
in San Mateo County in 2020. No mosquito samples or sentinel
chickens have been confirmed positive for WNV in San Mateo County
this year.
As of October 2, 2020, there have been 172 dead birds reported in
San Mateo County. Of those, 50 have been suitable for testing and
one has tested positive for West Nile virus (WNV). The WNV
positive bird was an American crow collected from South San
Francisco on September 22, 2020. This has been the only detection
of WNV in San Mateo County in 2020. No mosquito samples or
sentinel chickens have been confirmed positive for WNV in San
Mateo County this year.
Today (Oct. 1st) the District laboratory collected
mosquitoes in the area where
a dead crow infected with West Nile virus was found earlier
this week. These mosquitoes have all tested negative for West
Nile virus.
As of August 31, 2020, there have been 140 dead birds reported in
San Mateo County. Of those, 38 have been suitable for testing and
all 38 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have been confirmed positive
for West Nile virus in San Mateo County in 2020.
As of August 4, 2020, there have been 120 dead birds reported in
San Mateo County. Of those, 38 have been suitable for testing and
all 38 have tested negative for West Nile virus (WNV). To date,
there have been no confirmed West Nile virus detections in
mosquitoes or sentinel chickens in San Mateo County in 2020.
As of June 30, 2020, there have been 95 dead birds reported in
San Mateo County. Of those, 29 have been suitable for testing and
all 29 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2020.
As of May 31, 2020, there have been 68 dead birds reported in San
Mateo County. Of those, 23 have been suitable for testing and all
23 have tested negative for West Nile virus (WNV). No mosquito
pools or sentinel chickens have tested positive for West Nile
virus in San Mateo County in 2020.
In the 2019 calendar year, the District closed out one of its
lowest seasons for West Nile virus activity since the virus first
appeared in San Mateo County in 2004. No virus was detected
in the county this year in any of the standard WNV surveillance
indicators.
As of December 1, 2019, there have been 231 dead birds reported
in San Mateo County. Of those, 57 have been suitable for testing
and all have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
As of November 1, 2019, there have been 215 dead birds reported
in San Mateo County. Of those, 53 have been suitable for testing
and all 53 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
As of October 2, 2019, there have been 191 dead birds reported in
San Mateo County. Of those, 44 have been suitable for testing and
all 44 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
As of September 3, 2019, there have been 179 dead birds reported
in San Mateo County. Of those, 38 have been suitable for testing
and all 38 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
As of August 1, 2019, there have been 155 dead birds reported in
San Mateo County. Of those, 31 have been suitable for testing and
all 31 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
As of June 28, 2019, there have been 120 dead birds reported in
San Mateo County. Of those, 23 have been suitable for testing and
all 23 have tested negative for West Nile virus (WNV). No
mosquito pools or sentinel chickens have tested positive for West
Nile virus in San Mateo County in 2019.
As of June 3, 2019, there have been 86 dead birds reported in San
Mateo County. Of those, sixteen have been suitable for testing
and all sixteen have tested negative for West Nile virus (WNV).
No mosquito pools or sentinel chickens have tested positive for
West Nile virus in San Mateo County in 2019.
As of September 28, 2018, there have been 330 dead birds reported
in San Mateo County. Of those, 103 have been suitable for testing
and five have tested positive (5%) for West Nile virus (WNV). Two
mosquito pools have tested positive for WNV, both from East Palo
Alto during the month of August. Positive birds and pools for
2018 are summarized in the tables below. No sentinel chickens
have tested positive for West Nile Virus in San Mateo County in
2018.
As of August 31, 2018, there have been 291 dead birds reported in
San Mateo County. Of those, 91 have been suitable for testing and
five have tested positive (5%) for West Nile virus (WNV).
Additionally, two mosquito pools have tested positive for WNV,
both from East Palo Alto. Positive birds and pools for 2018 are
summarized in the tables below. No sentinel chickens have tested
positive for West Nile Virus in San Mateo County in 2018,
although a sentinel chicken in Santa Clara County, near the
border with San Mateo County, tested positive in August.
