A mosquito draws blood from a person's arm — a reminder of the health risks posed by rising mosquito populations and the importance of prevention.
Anaheim, California – Orange County is facing its first confirmed outbreak of West Nile virus this year after mosquito samples and a dead bird tested positive for the virus in Anaheim and Garden Grove. The discovery has prompted a public health advisory from the Orange County Mosquito and Vector Control District (OCMVCD), which is now ramping up mosquito surveillance and urging residents to take preventive measures.
The positive tests were found in four separate locations across the two cities, including neighborhoods near Euclid Avenue and the 5 Freeway in Anaheim, and around Brookhurst Street and Garden Grove Boulevard in Garden Grove. Though no human infections have been reported in the county so far this year, the combination of infected mosquitoes and a dead bird suggests the virus is now actively circulating in the area.
“Multiple mosquito samples and a dead bird testing positive for West Nile virus indicate that the virus is circulating in the community,” said Amber Semrow, Director of Scientific and Technical Services at OCMVCD. She added that Anaheim and Garden Grove are historically high-risk zones for the disease.
West Nile virus is transmitted primarily through the bite of infected mosquitoes, which themselves contract the virus by feeding on infected birds. Once rare in California, the virus is now entrenched throughout the state. As of July 18, 680 mosquito samples and 51 dead birds have tested positive statewide. Human infections have already been confirmed in Tulare, Stanislaus, and Kings counties.
Warm, stagnant summer conditions accelerate mosquito breeding and virus transmission, increasing the urgency of local prevention efforts. Orange County officials are now posting warning signs in affected neighborhoods and urging residents to eliminate sources of standing water, repair window and door screens, and use insect repellent when outdoors—especially around dawn and dusk, when mosquitoes are most active.
Brian Brannon, public information officer for OCMVCD, emphasized that one of the most effective steps residents can take is simply to “dump and drain” containers that collect water. “It’s the most environmentally friendly way to rid mosquitoes from our communities,” he said.
It’s a shift that feels almost surreal in a state that, not long ago, had virtually no mosquito-borne illness. Now, California’s densely populated regions—once too dry or temperate for mosquito outbreaks—are increasingly vulnerable. Public health officials say continued community vigilance will be key in keeping a manageable seasonal threat from becoming a full-blown public health crisis.
