West Nile Virus


West Nile virus is a reportable disease in Oklahoma. West Nile virus was first identified in the United States in the New York City area during the summer of 1999. Previously, this mosquito-borne virus had only been found in parts of Africa, Asia, Europe and the Middle East. The introduction of this foreign virus was recognized by deaths of thousands of birds (particularly crows and jays) and an epidemic of encephalitis in people and horses. Over the next few years, the virus rapidly expanded its geographic range.

When should I be aware of it in Oklahoma?
From 7 years of experience tracking West Nile virus in Oklahoma, we have learned that the West Nile virus season typically consists of the months of May to November.

Who is at risk for West Nile Virus?
Persons are at greatest risk of exposure to infected mosquitoes from July through October in our state. Persons of any age can develop symptoms of disease after being bitten by an infected mosquito, but those over the age of 50 are at greater risk of developing serious illness of the nervous system. During Oklahoma’s 7 year experience with West Nile virus, 318 confirmed cases of human disease have been reported; many cases required lengthy hospital stays and 20 Oklahomans have died from this virus.

What are the recommended controls for these mosquitoes?
The Oklahoma State Department of Health advises use of insect repellants- particularly those containing DEET, picaridin, oil of lemon eucalyptus [p-menthane 3,8-diol (PMD) or IR 3535] – when enjoying outdoor activities like gardening, yard work, camping, or other leisure activities. The type of mosquitoes that transmit West Nile virus are most active during evening and early morning hours.

Are there any precautions that I can take?
It is most important to take mosquito bite precautions during that time of the day. It is also recommended to drain or treat standing water around your home with a mosquito larvacide to reduce mosquito breeding sites.You can also report any possible sources in Oklahoma County of stagnant water that are breeding mosquitoes at our web site under complaints or through our office at 425-4347, 425-4348, or 425-4319.


In Oklahoma, mosquito season is typically from May to November. Mosquitoes are known to carry diseases, which include the West Nile virus, Chikungunya, and some types of encephalitis. In Oklahoma, the West Nile virus is the predominant mosquito-borne disease.

The Oklahoma State Department of Health updates the data for West Nile on their website weekly during mosquito season. For more information, please refer to the West Nile section of the OSDH website.

*For more information on terms and different types of West Nile Virus infections, please see our West Nile Virus FAQ section.

Here at OCCHD, we have an integrated strategy in place for Oklahoma County to control mosquitoes. We constantly and continually update this strategy by using many different kinds of data.

Individuals in Oklahoma County and the U.S. in general can reduce their risk of contracting the West Nile virus by getting rid of standing water around houses and by using insect repellant. Here is a simple way to remember how to “Fight the Bite” using the 3 D’s and a P of mosquito safety: