Garden Grove mosquito sample tests positive for West Nile virus

A batch of mosquitoes collected July 3 in Garden Grove has tested positive for West Nile virus, the county’s first positive tests this year, the Orange County Mosquito and Vector Control District confirmed Monday, July 9.

The batch of 117 mosquitoes, collected near Garden Grove Boulevard and Newhope Street, was the first of 1,882 samples examined by Vector Control since January to test positive for the virus.

West Nile virus is transmitted to humans and animals by infected mosquitoes that feed on dead birds carrying the virus. So far, there have been no confirmed human cases or dead birds reported in Orange County.

In most human cases, the virus is asymptomatic, but some people may experience fever, headache and body aches. In extreme cases, West Nile virus may require hospitalization and be fatal. Young children, the elderly and people with compromised immune systems are at a higher risk for infection.

A statement released by the public health agency said district staff will be surveying the surrounding area, notifying residents and working with city officials to identify infrastructure problems that could potentially create breeding grounds.

Mosquitoes need just a teaspoon of water to lay their eggs, said Mary-Joy Coburn, a Vector Control spokeswoman. The recent heat wave and humidity will accelerate their life cycle, she said, and may increase the number of potential carriers of the disease.

But, Coburn added, the agency expects a mild West Nile virus season because of the timing of the first positive tests.

“This being later, early July, that pretty much indicates it’s towards the end of the season,” Coburn said. “When it gets cooler again in October and November, then hopefully it will dwindle down too. Although, we have had cases in December.”

Last year, vector officials reported 38 confirmed human cases — including four deaths — and 280 samples of mosquitoes confirmed to be carrying the virus, in line with the annual average, Coburn said.

In 2014, a particularly bad year for West Nile virus in Orange County, there were 282 verified human cases and nine deaths.

West Nile virus first appeared in California in 2003 and is considered endemic to Orange County and much of Southern California because of the warm climate. Transmittance of the disease is more likely in the summer, because of the abundance of water-related activities.

“We have our gardens, we’re watering our plants. Kids are in the pool. There’s a lot of activities that generate water and it’s the standing water,” Coburn said. 

Vector Control advises people to empty containers filled with water at least once a week, to regularly clean bird baths and pet bowls and to dump all water from potted plant saucers to eliminate potential breeding grounds.

Officials advise the public to take the following steps to prevent mosquito bites:

• Apply mosquito repellents to exposed skin before going outside and to reapply as necessary.
• Use repellent containing DEET, Picaridin, IR3535, or oil of lemon eucalyptus.
• Close all unscreened doors and windows to prevent entry and repair all damaged screens to increase protection.
• Wear light-colored, long-sleeved shirts and long pants.

Residents are encouraged to call Vector Control if they see an unusually high number of day-biting mosquitoes. For more information, call the Orange County Mosquito and Vector Control District at 714-971-2421 or 949-654-2421, or visit ocvector.org.