West Nile Virus in Oklahoma
Mosquito Season 2007

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. By the end of 2005, West Nile virus had spread from the Atlantic to the Pacific coast with viral activity confirmed in all 48 contiguous states. Since national surveillance for this disease began in 1999, there have been a total of 23,974 human cases with 962 deaths reported to the Centers for Disease Control and Prevention (CDC) by 43 states through the ArboNet system.

Oklahoma began West Nile virus surveillance and testing of wild birds, mosquitoes, horses and people in 2001. West Nile virus was first found in northeastern Oklahoma in July 2002 and rapidly spread throughout the state. During Oklahoma’s five-year experience with West Nile virus, 201 confirmed cases of human disease have been reported; many cases required lengthy hospital stays and 12 Oklahomans have died from this virus. Over the past five years, state animal surveillance documented 1,200 equine cases and 1,230 test-positive birds. In 2005, the Oklahoma State Department of Health discontinued routine testing of dead wild birds as we now have a better understanding of the seasonal patterns and distribution of West Nile virus in the state. Higher rates of disease activity have occurred in the northwestern and northcentral regions of Oklahoma.

West Nile Virus Infections in Birds, Humans, Horses, and Mosquito Pools in Oklahoma, 2002-2006

 
From five years of experience tracking West Nile virus in Oklahoma, we have learned that the “West Nile virus season” consists of the months of 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 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. The Oklahoma State Department of Health advises use of insect repellants-- particularly those containing DEET, picaridin, or oil of lemon eucalyptus [p-menthane 3,8-diol (PMD)] -- 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, so 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.

For more information on West Nile Virus Prevention, please visit our Prevention Page

ADS Resources:
West Nile Virus General Information
West Nile Virus Resources for Healthcare Professionals
West Nile Virus Surveillance Data and Maps
West Nile Virus Helpful Link
Mosquito Control

Other Resources:
CDC West Nile Virus Page