CA Dept. of Public Health UC Davis Arbovirus Research and Training Mosquito and Vector Control Assoc. of CA

Case Counts by County

CountyDead birds
Alameda1
Alpine-
Amador-
Butte-
Calaveras-
Colusa-
Contra Costa-
Del Norte-
El Dorado-
Fresno4
Glenn-
Humboldt-
Imperial-
Inyo-
Kern-
Kings-
Lake-
Lassen-
Los Angeles12
Madera-
Marin-
Mariposa-
Mendocino-
Merced2
Modoc-
Mono-
Monterey-
Napa1
Nevada-
Orange4
Placer-
Plumas-
Riverside1
Sacramento42
San Benito-
San Bernardino-
San Diego-
San Francisco-
San Joaquin1
San Luis Obispo-
San Mateo-
Santa Barbara-
Santa Clara5
Santa Cruz-
Shasta-
Sierra-
Siskiyou-
Solano1
Sonoma-
Stanislaus4
Sutter-
Tehama-
Trinity-
Tulare1
Tuolumne-
Ventura-
Yolo2
Yuba-
Total81

WNV Activity by County
Printable Version
2020 | 2019 | 2018
2017 | 2016 | 2015
2014 | 2013 | 2012
2011 | 2010 | 2009
2008 | 2007

Data on this website are updated every Friday by 4pm. Due to different reporting schedules, case totals here may not always reflect those reported by local health departments. Updates during the off season (January-April) are less frequent.
April 17 - 23 is West Nile and Mosquito and Vector Control Awareness Week in California! This week highlights the importance of preventing mosquito bites and protecting Californians from mosquito-borne diseases. Stop by the "Fight the Bite" event at the State Capitol in Sacramento on Thursday, April 21st from 1:00 - 4:00pm for more information. Contact your local mosquito and vector control district to learn about events in your area.

Interactive Map

View the interactive map courtesy of http://maps.calsurv.org
- View Printable Map -

Total Counties with
WNV in 2020: 27

New counties highlighted in red.
Alameda, Amador, Butte, Fresno, Glenn, Imperial, Kern, Kings, Lake, Los Angeles, Madera, Merced, Napa, Orange, Placer, Riverside, Sacramento, San Diego, San Joaquin, Santa Clara, Shasta, Solano, Stanislaus, Sutter, Tulare, Yolo, and Yuba.

human cases

YTD: 10 Counties: 3
There were 5 new WNV human cases reported in California last week from Stanislaus County.

10 human cases from 3 counties have tested positive for WNV in 2020.

 

horses

YTD: 2 Counties: 2
There was 1 new WNV positive horse reported in California last week from Stanislaus County. This is the first WNV positive horse from Stanislaus County this year.

2 horses from 2 counties have tested positive for WNV in 2020.

 

dead birds

YTD: 81 Counties: 14
There were 17 new WNV positive dead birds reported in California last week from the following counties: Alameda (1), Los Angeles (4), Sacramento (10), and Yolo (2). This is the first WNV positive dead bird from Yolo County this year. This is the first indication of WNV from Alameda County this year.

81 dead birds from 14 counties have tested positive for WNV in 2020.

 

mosquito samples

YTD: 675 Counties: 23
There were 201 new WNV positive mosquito samples reported in California last week from the following counties: Butte (4), Fresno (30), Glenn (2), Kings (15), Los Angeles (45), Madera (7), Merced (6), Orange (8), Placer (10), Riverside (6), Sacramento (5), San Joaquin (13), Santa Clara (1), Shasta (4), Stanislaus (26), Sutter (4), Tulare (5), Yolo (9), and Yuba (1). This is the first indication of WNV from Glenn and Yuba counties this year.

675 mosquito samples from 23 counties have tested positive for WNV in 2020.

A mosquito sample may contain up to 50 individual mosquitoes.

 

sentinel chickens

YTD: 21 Counties: 4
There were 9 new WNV positive sentinel chickens reported in California last week from the following counties: Butte (2), Glenn (1), and Merced (6). This is the first indication of WNV from Glenn County this year.

21 sentinel chickens from 4 counties have tested positive for WNV in 2020.

Be a West Nile Watcher

Help us track down the West Nile Virus by reporting all dead birds. You can submit an online report by clicking on the button on the right.

2003-2019 WNV Activity Summary

Element 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Total
Human cases (fatal) 31 (0) 779 (29) 880 (19) 278 (7) 380 (21) 445 (15) 112 (4) 111 (6) 158 (9) 479 (20) 379 (15) 801 (31) 782 (53) 442 (19) 553 (44) 217 (11) 225 (6) 7,024 (309)
Horses 12 540 456 58 28 32 18 19 15 22 23 153 193 213 21 11 15 1,314
Dead birds 96 3,232 3,046 1,446 1,396 2,569 515 416 688 1,644 1,251 2,442 1,349 1,352 510 501 226 22,679
Mosquito samples 32 1,136 1,242 832 1,007 2,003 1,063 1,305 2,087 2849 2,528 3,340 3,329 3,528 3,371 1,963 3,288 34,903
Sentinel chickens 70 809 1,053 640 510 585 443 281 391 540 485 443 449 343 305 163 139 7,649
Squirrels - 49 48 32 26 32 10 24 24 23 03 03 03 03 03 03 03 276
1 There were 20 imported human cases. 2 There were 3 imported horse cases. 3 Not monitored this year.

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Compared to previous year and previous five-year average to date

As of Aug 07, 2020202020195Y AVG
Counties272332
Human cases101024
Dead birds8158370
Mosquito samples67516441638
Sentinel chickens211069
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2020 YTD activity -

WNV Reports

Weekly Report

08.12 2020 YTD SLEV Activity Map
08.07 Arbobulletin #17
08.07 2020 YTD WNV Activity Map

Humans

08.07 2020 Human WNV Incidence Report
08.07 2003-2020 WNV Case Summary
03.02 2019 Human WNV Incidence Report

Dead Birds

08.07Reported, Tested, Positive 2020
08.07Positive Species for 2020
08.07Positive Counts by City/County for 2020

Mosquitoes

10.04 AMOR - EVS Week 39
10.04 AMOR - GRAVID Week 39
10.04 AMOR - NJLT Week 39
- view report archives -