West Nile Virus

West Nile virus (WNV) is a reportable disease in Oklahoma. WNV 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 spread across the United States.

In Oklahoma, the WNV season runs from May to November.  Persons are at greatest risk of exposure to infected mosquitoes from July through October in our state.  Persons of any age can become ill after being bitten by an infected mosquito, but those over the age of 50 are at greater risk of developing serious illness involving the nervous system.  Over 80% of people infected with the virus never become ill.  If people do become ill, most cases are mild with symptoms such as a fever, headache, tiredness and body aches that go away on their own.  Some people may develop a rash on the trunk of the body.  In more severe cases, persons can develop meningitis or other neurologic disease.

The Oklahoma State Department of Health advises use of insect repellents—particularly those containing DEET, picaridin, oil of lemon eucalyptus (PMD), or IR 3535—when enjoying outdoor activities like gardening, yard work, camping, or other leisure activities.  The type of mosquitoes that transmit WNV are most active during early morning and evening hours, so it is 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.

West Nile virus Surveillance Data and Statistics:  2012

West Nile Virus Cases and Deaths by Year, 2002-2012 (33k.pdf)

West Nile Virus Disease, Hospitalizations, Deaths and Positive Blood Donors, 2012 (73k.pdf)

West Nile Virus Cases by Age Group, 2012 (70k.pdf)

Map: Number of West Nile Virus Cases by County (284k.pdf)

Map: Rate of West Nile Virus By County (267k.pdf)

West Nile virus Fact Sheets and Information:

West Nile Virus Fact Sheet (150k.pdf)
   Virus del Nilo Occidental Hoja Informativa (48k.pdf)
West Nile Virus Questions and Answers
Mosquitoborne Disease Prevention Tips
Insect Repellent Fact Sheet (55k.pdf)

News Release: McAlester Couple’s Lives Change After West Nile Virus Strikes

West Nile virus Healthcare Provider Resources:

Physician Instructions for Testing

External West Nile virus Resources:

West Nile Virus (CDC)
Arboviral Encephalitides (CDC)
Pesticides and Mosquito Control (EPA)
Animal Health Monitoring and Surveillance (USDA)
Mosquitoes and West Nile Virus (OSU)
West Nile Virus Blood Transfusion Questions & Answers (CDC)
The National Pesticide Information Center - West Nile Virus (NPIC)
American College of Physicians West Nile Virus Education Resource
National West Nile Activity Map (USGS)

This page last updated March 28, 2013.