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Healthy Outlook

Mosquito Prevention is Key to Avoiding West Nile Virus

By Erika Jenssen, MPH

Wednesday, July 30, 2014

Nearly a decade has passed since West Nile Virus first popped up on the local news. Now every summer we hear about dead birds and spraying to control mosquitos.

But the important part is that we can take action to protect ourselves and others around us. Despite the exotic-sounding name, West Nile Virus is part of life in California, and it has been for years.

There is no cure, or a vaccine to prevent it. But there is only one way to catch it. Mosquito bites spread West Nile Virus, so the best way to avoid the disease is to reduce our exposure to these blood-sucking pests.

West Nile infects several kinds of animals, especially birds. When a person catches the disease, it’s usually because a mosquito drank the blood of an infected bird, then afterward bit the person and passed along the virus. People, birds and other animals cannot pass it to each other, or to other members of their own species.

That is why we now hear about dead birds being found in our county and elsewhere in the Bay Area, and sometimes about trucks “fogging” areas at night to kill mosquitos. Not surprisingly, West Nile season mirrors mosquito season, with most infections happening from early summer to fall.

The Contra Costa Mosquito & Vector Control District sets out traps for mosquitos all over the county, and studies dead birds to find out why they died. When they find the virus in birds or mosquitos from a particular area, we know that West Nile Virus is probably making the rounds there.

One way anyone can help keep their community safe is to drain any standing water in the yard or home. Mosquitos lay eggs in still water, so any little basin where water collects could quickly become a local hatchery. That’s especially true of neglected ponds and swimming pools.

If you need help mosquito-proofing your property, or know about a potential source of mosquitos in your neighborhood, please call 925-685-9301 or visit Anonymous reports are accepted.

Another way to help is to let the state know about any dead birds or squirrels in the neighborhood, so they can be tested. California has a hotline for reporting them at 1-877-968-2473.

Finally, consider precautions to lower the chance of being bitten. Mosquitos are most active at dawn and dusk, so those might be good times to stay indoors. Bug repellent with DEET, Picaridin or the oil of Lemon Eucalyptus also helps.

West Nile Virus can be dangerous, and some people do get very sick or even die from it. People over 50 and people with compromised immune systems are at highest risk.

But it is rare to get sick from this disease. As of July 4, only nine human cases have been reported in California this year, including one from Contra Costa County.

In fact, many of us may have already had West Nile without knowing it and are immune already. Only one in five infected people ever develop symptoms, which can include fever, aches and swollen lymph glands.

So don’t be afraid of the disease with the exotic name. Use your head, and avoid mosquitos when possible – not that you needed another reason!

For up-to-date information about reported West Nile Virus infections, visit

Healthy Outlook is written by the professional staff of Contra Costa Health Services, the county health department. Send questions to series coordinator Dr. David Pepper at For more health information, go to
About the Author
Erika Jenssen is the Director of the Communicable Disease Programs for Contra Costa Health Services.