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OCINT

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ACTIVESEV 3 · HIGHUPDATED about 4 hours ago
▸ SITUATION

OC West Nile Season Escalates: 21 Human Cases, Record Mosquito Positives and a First Death Reported by an Anaheim Family

Orange County's 2026 West Nile virus season is the worst in years: ABC7 cited 21 human cases countywide as of late September (versus one at the same point in 2025) and OCMVCD reports a record 757 WNV-positive mosquito samples, 165 of them in Anaheim. The family of Daniel Clavel, 61, of Anaheim, says he died in mid-September after 24 days in intensive care; OCHCA says it is investigating and has not yet posted a 2026 death. OCMVCD has run three waves of overnight truck spraying.

MACHINE-READABLE markdown · JSON

CITIES AFFECTED
ANAHEIMBUENA PARKFULLERTONGARDEN GROVEHUNTINGTON BEACHORANGESTANTONTUSTINWESTMINSTER
STARTED
2 months ago
Jul 26, 2026, 17:00 PT
EVIDENCE
10 items · 4 areas
SITUATION MAP
4 areas · 10 signals
WHO

Orange County residents, particularly in Anaheim and other heavily affected cities; OCHCA and OCMVCD are leading public health and vector control response.

WHAT

West Nile virus outbreak with 21 reported human cases and one confirmed death in OC in 2026; record 757 WNV-positive mosquito samples countywide, including 165 in Anaheim.

WHERE

Countywide across Orange County; heaviest mosquito activity in Anaheim, Fullerton, Cypress, Buena Park, and La Habra.

WHEN

Season began early in summer 2026; first human death reported mid-September 2026; season peak through September.

WHY

Unprecedented mosquito activity — more than twice the 2014 epidemic-year positive-sample count — has driven elevated human transmission risk throughout the summer.

▸ NARRATIVE
Current Status

Orange County's 2026 West Nile virus (WNV) season has recorded its first confirmed human death. ABC7 reported on September 23, 2026 that an Anaheim man, 61, died in mid-September after spending 24 days in intensive care with West Nile virus contracted in August. OCHCA stated it was investigating the case and had not yet posted the death to its dashboard at time of reporting. ABC7 cited 21 confirmed human OC cases this season — up from 11 recorded on OCHCA's dashboard as of September 3 — compared to one case at the same point in 2025.

OC recorded only three total human WNV cases in all of 2025. No resolution is expected before the end of peak transmission season.

Scope of Detections

OCMVCD has now documented 757 WNV-positive mosquito samples countywide in 2026 — a new record — with 165 samples in Anaheim alone, the most of any city, according to ABC7. This far surpasses the prior figure of 300+ samples reported in early September, which was itself described as more than twice the count from the 2014 epidemic year. WNV-positive mosquito pools have been confirmed in at least 10 cities across Orange County, with the heaviest activity in Fullerton, Anaheim, Cypress, Buena Park, and La Habra. Statewide, CDPH counted 65 symptomatic human cases as of August 28 (per LA County DPH arboviral report, Sept. 4).

Vector Control Operations

OCMVCD completed three waves of overnight truck-mounted ULV adulticiding through early September:

  • Wave 1 (Aug. 18–20): La Habra, Buena Park, Fullerton, Anaheim, Garden Grove — DeltaGard and AquaDuet.
  • Wave 2 (Aug. 26–28): Huntington Beach, Westminster, Garden Grove, Stanton, Anaheim, Buena Park, Cypress, Orange, La Palma.
  • Wave 3 (Sept. 2–4): Anaheim/Garden Grove/Stanton, Buena Park/Cypress/La Palma, Los Alamitos/Rossmoor.

All operations ran midnight to 5:30 a.m. OCMVCD noted operations may continue if mosquito counts persist.

Elevated Risk: Immunocompromised Patients

The August 11 CAHAN advisory specifically calls out patients on B-cell-depleting or B-cell-modulating therapies as facing heightened risk of severe neuroinvasive disease from WNV and other arboviruses. Clinicians are advised to maintain heightened suspicion when evaluating febrile or neurologically symptomatic patients in this population.

What to Watch

Key indicators for further escalation include: additional confirmed human deaths, expansion of positive detections beyond current footprint, and the statewide case trajectory. The OCHCA West Nile dashboard is the authoritative source for updated OC case counts. westnile.ca.gov tracks the statewide picture.

This page is a public-health Situation for situational awareness. It is not medical advice and is not an emergency-notification service. Follow OCHCA and your clinician for personal guidance.

▸ EVENT TIMELINE
14 moments
  1. Jul 3, 01:41(3 months ago)

    OC Register reports WNV-positive mosquitoes now confirmed in 10+ cities across Orange County.

    NEWOC Register: More mosquitoes found infected with West Nile …
  2. Jul 27, 13:00(2 months ago)

    Voice of OC reports OCMVCD warning of West Nile virus amid escalating mosquito activity.

    NEWVoice of OC: Orange County Mosquito Control Warns of West N…
  3. Jul 29, 16:18(2 months ago)

    OCHCA issues CD Health Alert characterizing 2026 WNV activity as 'early and intense' and announcing new WNV diagnostics.

    HTHOC Health: CD HEALTH ALERT: Early and Intense West Nile Vir…
  4. Jul 30, 02:12(2 months ago)

    NWS issues Extreme Heat Warning for Orange County Inland areas, compounding outdoor exposure risk.

    WTHExtreme Heat Warning — Orange County Inland
  5. Aug 3, 12:21(about 2 months ago)

    OCHCA publishes additional public outreach on mosquito prevention messaging.

    HTHOC Health: Mosquitoes. More Than Just a Nuisance.
  6. Aug 6, 09:50(about 2 months ago)

    OCHCA confirms first human WNV case of the 2026 season: an Anaheim resident.

    HTHOC Health: CD HEALTH ALERT: First West Nile Virus Human Cas…NEWCBSLA: Orange County confirms first human West Nile virus c…
  7. Aug 11, 15:44(about 2 months ago)

    OCHCA issues CAHAN Disease Advisory flagging elevated WNV neuroinvasive disease risk for patients on B-cell-depleting or B-cell-modulating medications.

    HTHOC Health: CAHAN Disease Advisory – Risk of Severe Arbovira…
  8. Aug 14, 07:03(about 2 months ago)

    ABC7 reports heat relief moving into SoCal, providing a modest break from the extreme heat that had compounded outdoor exposure risk.

    NEWABC7: SoCal is finally getting relief from the heat. Here's…
  9. Aug 18, 00:00(about 1 month ago)

    OCMVCD begins overnight truck-mounted adulticiding operations (midnight–5:30 a.m., Aug 18–20) in La Habra, Buena Park, Fullerton, Anaheim, and Garden Grove using DeltaGard and AquaDuet. Statewide case count at 30 as of Aug 14; OC remains at one human case.

  10. Aug 26, 00:00(about 1 month ago)

    OCMVCD begins second wave of overnight truck-mounted adulticiding (midnight–5:30 a.m., Aug 26–28) expanding to Buena Park, Anaheim/Buena Park/Cypress, Anaheim/Orange, Garden Grove/Stanton/Westminster, and Huntington Beach/Westminster.

  11. Sep 2, 00:00(27 days ago)

    OCMVCD conducts third wave of overnight truck-mounted ULV adulticiding (midnight–5:30 a.m., Sept. 2–4) covering Anaheim/Garden Grove/Stanton, Buena Park/Cypress/La Palma, and Los Alamitos/Rossmoor areas.

  12. Sep 2, 17:00(26 days ago)

    OCHCA West Nile dashboard (data as of Sept. 3) records 11 confirmed human WNV cases and 0 deaths in OC for 2026 — up sharply from one case as of Aug. 6, and above zero cases at the same date in 2025.

  13. Sep 4, 22:50(24 days ago)

    ABC7 reports below-average temperatures continuing in SoCal, with Hurricane Marie bringing a chance of rain — cooler conditions may modestly slow mosquito breeding but do not end peak WNV transmission risk.

    NEWABC7: SoCal is finally getting relief from the heat. Here's…
  14. Sep 22, 17:00(6 days ago)

    ABC7 reports the first confirmed WNV death in OC's 2026 season: an Anaheim man, 61, died in mid-September after 24 days in intensive care. OCHCA said it was investigating and had not yet posted the death. ABC7 cited 21 total OC human cases this season and a record 757 WNV-positive mosquito samples countywide, with 165 in Anaheim.

    NEWABC7: Orange County man dies after contracting West Nile vi…
▸ EVIDENCE
10 items
  1. NEW5 days ago
    ABC7: Orange County man dies after contracting West Nile virus, family says

    The family of an Orange County man says he died after contracting West Nile virus and is sharing his story in hopes of warning others about the risks associated with the disease.

  2. NEW14 days ago
    ABC7: SoCal is finally getting relief from the heat. Here's how long it will last

    Southern California is getting a much-needed break from the heat as a low-pressure system lingers over the region after days of scorching temperatures.

  3. HTHabout 2 months ago
    OC Health: CAHAN Disease Advisory – Risk of Severe Arboviral Disease in Patients Receiving B Cell-Depleting or Modulating Medications

    CAHAN Disease Advisory – Risk of Severe Arboviral Disease in Patients Receiving B Cell-Depleting or Modulating Medications August 11, 2026 eric.shearer Tue, 08/11/2026 - 15:44 Body The Centers for Disease Control and Prevention (CDC) is issuing this Health Alert Network (HAN) Health Advisory to shar

  4. NEWAnaheimabout 2 months ago
    CBSLA: Orange County confirms first human West Nile virus case of 2026

    Orange County Health Care Agency confirmed the county's first human West Nile case of 2026 in an Anaheim resident. Officials have described the mosquito season as potentially one of the worst on record.

  5. HTHabout 2 months ago
    OC Health: CD HEALTH ALERT: First West Nile Virus Human Case of the 2026 Season Reported

    CD HEALTH ALERT: First West Nile Virus Human Case of the 2026 Season Reported August 6, 2026 eric.shearer Thu, 08/06/2026 - 09:50 Body A resident of Anaheim has tested positive for West Nile Virus (WNV), becoming the first human WNV infection in Orange County this year. In 2025, Orange County had th

  6. HTHabout 2 months ago
    OC Health: Mosquitoes. More Than Just a Nuisance.

    Mosquitoes. More Than Just a Nuisance. August 3, 2026 kai.lin Mon, 08/03/2026 - 12:21 Body Image Health_Corner_Website_Dr_Zimmerman_Header.png Summer is here and with that comes mosquito season. Did you know that mosquitoes are responsible for more human deaths than any other animal in the world? Th

  7. WTH2 months ago
    Extreme Heat Warning — Orange County Inland

    Extreme Heat Warning issued July 30 at 2:12AM PDT until August 2 at 8:00PM PDT by NWS San Diego CA

  8. HTH2 months ago
    OC Health: CD HEALTH ALERT: Early and Intense West Nile Virus Activity; New West Nile Virus Diagnostics

    CD HEALTH ALERT: Early and Intense West Nile Virus Activity; New West Nile Virus Diagnostics July 29, 2026 mi.le Wed, 07/29/2026 - 16:18 Body Key Messages:Multiple detections of West Nile Virus (WNV)-positive mosquitoes in Orange County and a much higher-than-usual number of human WNV cases in Calif

  9. NEW2 months ago
    Voice of OC: Orange County Mosquito Control Warns of West Nile Virus

    Orange County sign in Brea. " data-large-file="https://i0.wp.com/voiceofoc.org/wp-content/uploads/2021/08/OC_leopo.jpg?fit=771%2C434&ssl=1" /> West Nile Virus is spreading across Orange County as the season’s temperatures rise. Voice of OC is Orange County's nonprofit newsroom. We rely on donations

  10. NEW3 months ago
    OC Register: More mosquitoes found infected with West Nile in Orange County, now in 10 cities

    “In a five-year average of mosquito abundance, we’re off the charts,” a spokesman for the Orange County Mosquito and Vector Control District said.

▸ SOURCES
10 links