How to keep from being infected by West Nile virus, after mosquito bite kills Contra Costa man

After a Contra Costa man’s death from West Nile virus was reported on July 16, the county Health Department is urging the public to take precautions against the mosquito-borne illness.

It was the county’s first reported West Nile death since 2006, and California’s only death among five recorded cases this year.

Citing privacy laws, the county has released little information about the death, except that the man lived in the eastern part of the county and that health officials have not determined where he contracted the illness. But the Contra Costa Mosquito & Vector Control District has confirmed that four dead birds have tested positive for West Nile — three in Concord and one in Oakley, as well as five sentinel chickens, all of which were at the same Oakley location. The county has found no positive mosquito samples yet. 

Steve Schutz, scientific programs manager at the Mosquito & Vector Control District, said that while most cases are mild, West Nile virus can damage the brain and nervous system, causing long term disabilities. 

The virus is known to be more prevalent in the warmer parts of California, specifically in Southern California and the Central Valley, but has been prevalent statewide since 2005. 

The first human cases in California were detected in 2003, according to state Public Health Department records. Since then, 8,121 cases have been reported in California, including 395 fatalities.

Across the country, 72 people have tested positive for the virus, with double-digit cases in Nevada, Texas and Nebraska, Centers for Disease Control and Prevention records show. Nearly 3,000 people in the U.S. have died from the disease since 1999. 

Virus activity varies from year to year, Schutz said, due in part to rainfall. California has experienced two consecutive wet winters with heavy, and in some places record-breaking, rainfall. Mosquitos breed in wet places.

As the summer progresses, the population of infectious mosquitoes goes up, raising the risk of mosquito-borne diseases, said William K. Reisen, professor emeritus at the School of Veterinary Medicine at UC Davis. People who are older or are immunocompromised are at higher risk of a serious infection, he added.

Dr. Meera Sreenivasan, deputy county health officer, called the Contra Costa death a tragedy, adding in a news release that it “reinforces how important it is to reduce risk of West Nile virus infection by reducing our exposure to mosquitos.” 

The Contra Costa Mosquito & Vector Control District routinely monitors for the virus by testing dead birds, mosquito samples and flocks of sentinel chickens.

To reduce your risk of becoming infected:

• Avoid mosquito bites by wearing long sleeves and using insect repellent when outdoors.
• Remove sources of stagnant water which can be a habitat for mosquito larvae.
• Install window screens.
• Report any dead birds to the California Dead Bird Call Center at 877-968-2473.

Symptoms of West Nile virus may be mild and include a fever, headache, body aches, nausea and possibly a rash. In rare cases, the virus affects the brain and nervous system, causing meningitis or encephalitis, with additional symptoms such as neck stiffness, vision loss, paralysis and confusion.

But most of those infected by West Nile virus have no symptoms, and the virus rarely is transmitted from person to person. 

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