The Orange County Mosquito and Vector Control District (OCMVCD) has confirmed that mosquitoes collected in the City of Santa Ana have tested positive for West Nile virus (WNV). These are the first samples to test positive in the Santa Ana this year.
The positive mosquitoes were collected in an area generally bounded by St. Andrew Pl., Grand Ave., E. Dyer Rd., and S. Kilson Dr. in Santa Ana.
West Nile virus is primarily transmitted to humans through the bite of infected mosquitoes, which acquire the virus when feeding on infected birds. At present, Orange County has not reported any human cases of West Nile virus.
“Multiple mosquito samples testing positive for West Nile virus indicate that the virus is circulating in the community,” said OCMVCD Director of Scientific and Technical Services Amber Semrow. “Santa Ana is historically a high-risk area for West Nile virus activity. Conditions across the region are favorable for sustained virus activity during the warm summer months.”
OCMVCD staff will continue to conduct surveillance, inspections, and control measures for mosquitoes in the area to prevent additional mosquito breeding. OCMVCD will also post WNV advisory signs alerting residents of WNV activity in the affected area.
“Everyone in Orange County should work together to fight mosquitoes,” said OCMVCD Public Information Officer Brian Brannon. “Dumping and draining standing water is the most effective way to rid mosquitoes from our communities,”
To prevent mosquito bites, take action and follow these tips:
- Dump and drain containers holding water at least once a week
- Clean and scrub bird baths and pet water bowls
- Wear repellent containing DEET, Picaridin, IR3535, or oil of lemon eucalyptus
- Close all unscreened doors and windows to prevent mosquitoes from entering your home or space; repair broken or damaged screens
- Wear light-colored, loose-fitting, long-sleeved shirts, and long pants while outside at dawn and dusk
For more information about prevention, visit www.ocvector.org.
West Nile virus (WNV) can affect anyone, but certain demographics are more vulnerable to severe illness. Here’s a breakdown of who is most impacted:
General Risk
- All individuals in areas where WNV is active are at risk, especially during mosquito season (summer through early fall).
- People who spend a lot of time outdoors, such as workers or recreational enthusiasts, are more likely to be exposed to mosquito bites.
High-Risk Demographics for Severe Illness
- Older Adults
- People over the age of 50, and especially those over 60, are at significantly higher risk of developing severe forms of the disease, such as West Nile neuroinvasive disease (WNND), which includes encephalitis and meningitis.
- Immunocompromised Individuals
- Those with weakened immune systems—such as organ transplant recipients, cancer patients, or individuals on immunosuppressive therapy—are more likely to experience severe symptoms.
- Men
- Some studies have found that male patients are more likely to develop WNND and have higher mortality rates compared to females.
- People with Pre-existing Conditions
- Conditions like diabetes, hypertension, and kidney disease have been associated with worse outcomes in WNV infections.
- Residents in Rural or Endemic Areas
- People living in rural or semi-rural areas where mosquito control may be less effective are at increased risk.
Severity and Outcomes
- About 1 in 150 infected individuals develop severe illness.
- Among those with WNND, hospitalization rates exceed 80%, and case fatality rates can range from 3% to over 20%, especially in older adults.