Figures change through the season. Check the live CDPH and county dashboards linked below for current counts. Every number here is a snapshot with its source and date attached. Current-year counts are provisional and get revised.
The statewide picture
As of October 2, 2026, the California Department of Public Health (CDPH) reported 252 human West Nile virus cases in 23 counties and 19 deaths. The same update listed 702 dead birds, 3,839 mosquito samples, 149 sentinel chickens, and 14 horses. CDPH describes this as the "highest levels of West Nile virus activity in five years."
For comparison, the state's history table shows 117 cases and 11 deaths for all of 2025. The 2026 case count has already more than doubled that, and the season is still open. For why this year runs so heavy, see why California's 2026 season is so active.
Where the cases are
The state's county table dated October 6, 2026 shows these human case counts, among others:
- Los Angeles: 111
- Orange: 23
- Fresno: 19
- Butte: 13
- Sacramento: 11
- Kings: 11
- Kern: 10
- Stanislaus: 7
- San Diego: 5
- Yolo: 5
- Glenn: 5
- Ventura: 0
The state's weekly report lists deaths by jurisdiction: Los Angeles 4, Orange 4, Butte 3, Glenn 2, Sacramento 2, Yolo 2, Kings 1, and Tuolumne 1.
The national line
Across the US, CDC ArboNET provisional data as of October 6, 2026 shows 1,172 West Nile disease cases and 70 deaths. The same file shows California at 250 cases and 19 deaths; 214 of those 250 cases were neuroinvasive, the severe form. The state's own count is 252. The two counts are compiled differently and on different schedules, so small gaps are expected. Outside California, the NPIC list linked in Sources points you to your local mosquito control agency.
How to read these counts
Counts reflect people who were tested
A human case can be counted only after someone is tested and the positive result is reported to public health. CDC's national system, ArboNET, collects those reports from the states.
CDC says about 80% of infected people have no symptoms. People without symptoms have little reason to get tested, so official counts are unlikely to capture every infection. Read any case count as reported cases, not as everyone who was infected.
County and state counts differ
LA County Public Health's report #9, dated October 2, 2026, lists 180 infections and 5 deaths, and that figure excludes Long Beach and Pasadena. The state table dated October 6 shows Los Angeles at 111 cases, and the state's weekly report lists 4 deaths there.
Neither number is wrong. The county report counts "infections" and the state table counts "cases," and the two counts are compiled differently and on different schedules. Orange County shows the same kind of gap: the OC Health Care Agency reported 36 infections and the county's first 2026 deaths, in older adults, on September 29, 2026, while the state table lists Orange at 23 cases.
When the numbers disagree, note the date and the word each source uses, and compare like with like.
What 80%, about 20%, and less than 1% mean
CDC's symptom figures describe what happens to people who are infected:
- About 80% have no symptoms.
- About 20% develop a fever and other flu-like symptoms.
- Less than 1% develop severe illness affecting the central nervous system.
These are shares of infections, not shares of the public. Case tables look different: in CDC's provisional ArboNET file dated October 6, 2026, 214 of the 250 CDC-counted California cases were neuroinvasive, the severe form.
Who is at higher risk
CDC says the risk of severe illness rises with age. People 65 and older and people with certain medical conditions are at higher risk. If you or someone in your household has symptoms, or you are unsure whether a health condition applies, talk with a clinician. This article explains public data. It is not medical advice.
Why a county with zero cases still matters
Ventura County shows 0 human cases on the October 6 state table. The same table shows 7 dead birds and 1 mosquito sample in the county.
Surveillance tests birds and mosquitoes because they show where the virus is circulating, whether or not anyone has been reported sick. A bird or mosquito sample on the state table means the virus has been found locally. Zero human cases is good news. It is not the same as zero virus.
What to do with this information
- Check your own county's dashboard and the state table. Note the date on each and whether it counts cases or infections.
- Treat a local bird or mosquito detection as your cue. That is the signal to cut down on bites outdoors, especially from dusk to dawn, when CDC says adult Culex mosquitoes are most active.
- Use an EPA-registered repellent and follow the label. Fewer bites means fewer chances of exposure.
- Walk your yard once a week. Tip, scrub, or cover anything holding water. The ten-minute weekly yard check lays out the route.
- Call your local vector control program. Many districts inspect private property on request at no charge and give away mosquitofish.
- Report dead birds through your county or state's dead-bird reporting line. Those reports feed the surveillance numbers above.
- Take symptom questions to a clinician, especially for anyone 65 or older or with a medical condition. This article is not medical advice.
What the county does vs what you do
| The vector control program | You, on your property |
|---|---|
| Traps and tests mosquitoes, and tracks dead birds, sentinel chickens, and horses | Report dead birds so they can be tested |
| Publishes counts on a dashboard that changes week to week | Read the date and the definition before sharing a number |
| Inspects private property on request in many districts, often free | Ask for a visit if you see standing water you cannot reach |
| Treats breeding sources and offers free mosquitofish in many districts | Tip and scrub saucers, buckets, and toys every week |
| Public health tracks reported human cases | Call a clinician about symptoms, not a dashboard |
- CDPH, West Nile Virus website — westnile.ca.gov
- CDPH, 2026 county case counts — westnile.ca.gov
- CDC ArboNET provisional data via CDPH — westnile.ca.gov
- CDC, West Nile Virus Data and Maps — www.cdc.gov
- CDC, Symptoms of West Nile Virus — www.cdc.gov
- CDC, About Culex Mosquitoes — www.cdc.gov
- LA County Public Health, 2026 arbovirus report — publichealth.lacounty.gov
- OC Health Care Agency, first 2026 West Nile deaths — ochealthinfo.com
- NPIC, Mosquito control agencies by state — npic.orst.edu/vector_agencies.html