As of 30 October 2026, California reported 502 human cases of West Nile virus (WNV) disease across 24 counties, including 31 deaths – the highest annual case count since 2017. Of these, 429 cases (85%) involved neuroinvasive disease. The median age of case patients was 66 years and 326 (65%) of the case patients were male. The dates of symptom onset ranged from June 8 to October 16. Los Angeles County was particularly affected, accounting for 293 cases (58%) and 12 deaths.
Nationwide, the US CDC reported 1’668 human WNV cases across 47 states as of 3 November 2026, with California accounting for approximately 30% of all reported cases.
- Protect yourself against mosquito bites during the day and at night (see factsheet mosquito and tick bite protection).
- Do not touch sick or dead birds, as they may also be infected.
- If you have visited a West Nile fever transmission area, do not donate blood for at least 28 days after returning.