Pasadena Public Health reported the city's first two human West Nile virus cases of 2026 on Thursday, though confirmation testing on the samples is still pending. The cases meet clinical and initial laboratory criteria for the virus, but health officials say they are still awaiting final lab results before confirming the diagnoses.
Pasadena's health department made the announcement as part of a broader statewide and county-level surge in virus activity. According to the Pasadena Public Health Department, California had reported 452 human West Nile virus cases and 29 deaths across 24 counties as of October 23, including 251 cases in Los Angeles County alone. That is a dramatic jump from the same point last year, when the state had logged just 67 cases across 15 counties, the department said.
Statewide Activity Hits a Five-Year High
The surge isn't isolated to Pasadena. The city's health department has separately noted that West Nile virus activity statewide has reached its highest level in five years, a benchmark tracked by the California Department of Public Health. Regional mosquito control agencies have echoed that warning, with Greater Los Angeles County Vector Control District describing virus activity as elevated across the broader Los Angeles region this year.
Closer to home, the San Gabriel Valley has seen its own spike. As of September 3, virus activity in the valley had already surpassed its five-year average, the Pasadena Star-News reported, with 105 virus-positive mosquito samples detected in the area by that date. The San Gabriel Valley Mosquito and Vector Control District, which has tracked virus activity in local mosquito populations since 2003, works with Pasadena's public health department to help control mosquitoes in public spaces.
No Pasadena Cases Since Last Year
Before Thursday's announcement, the last confirmed West Nile virus case in a Pasadena resident dated back to 2025, the city's health department noted. The virus spreads to people through the bite of an infected mosquito, and most people who get infected never develop symptoms at all — about 80% of infections produce no symptoms, according to the department. But a small percentage of those infected can develop a potentially life-threatening illness, with symptoms ranging from a mild flu-like illness to severe disease affecting the central nervous system that can require hospitalization or, in rare cases, prove fatal. There is currently no vaccine or cure for West Nile virus disease.
California's surge this year isn't confined to the Los Angeles area. In San Joaquin County, public health officials confirmed their first human case of 2026 back in August, involving a woman in her 60s — at the time, the 12th reported case statewide, according to San Joaquin County Public Health Services. Stanislaus County also reported its first case of the year, with statewide totals at that point sitting at 46 cases and four deaths, compared with just 14 cases at the same time in 2025, according to a report from CBS Sacramento.
How Pasadena Residents Can Protect Themselves
Pasadena Public Health is urging residents to take precautions against mosquito bites as the virus continues to circulate. Officials recommend wearing protective clothing and using insect repellent containing picaridin, DEET, oil of lemon eucalyptus or PMD, or IR3535. The department also advises residents to tip out stagnant water around the home weekly, toss unused containers that can hold standing water, and repair or install window screens to keep mosquitoes out.
Birds can also carry the virus, and some become seriously ill or die from it, the health department noted. Officials are encouraging residents to report dead birds to help track the virus's spread, which can be done through the California West Nile virus website or by calling 1-877-WNV-BIRD (968-2473). As first reported by the Los Angeles Daily News, Pasadena's two newly reported cases remain unconfirmed pending final lab results, even as the statewide case count continues to climb well beyond last year's pace.
