West Nile Virus cases in Oklahoma

The first cases of West Nile virus (WNV) in Oklahoma were confirmed in Okfuskee and McIntosh counties in early June.

The Oklahoma State Department of Health (OSDH) encourages residents to take precautions to reduce the risk of contracting WNV, a mosquito-borne illness. WNV is spread through the bite of the Culex mosquito, which feeds on infected birds and transmits the virus when biting humans, horses and some other mammals. This type of mosquito increases in numbers during mid-to-late summer when the temperatures climb and the weather pattern is drier.

Floodwater mosquito populations created  by recent rain in Oklahoma do not increase the risk of WNV.  The type of mosquitoes that hatch after severe flooding are primarily the species of mosquitoes classified as “nuisance mosquitoes.” They bite aggressively and cause lots of itchy bites, but they are not typically involved with transmission of diseases.

Floodwater mosquito populations tend to die out three weeks after the rains stop and the sun dries out affected low lying areas.

Summertime typically marks the beginning of the WNV season in Oklahoma, with outdoor activities providing opportunities for encountering infected mosquitoes. Although the severity of this year’s WNV season cannot be predicted, it is important to know the highest risk months in Oklahoma for WNV exposure occur from July through October.  Since WNV was introduced into Oklahoma, there have been 3 outbreak years – 2003, 2007 and 2012. All three of these seasons were characterized by higher than normal summer temperatures and drought.

Symptoms of WNV include sudden onset of fever, headache, dizziness and muscle weakness. Long-lasting complications can include difficulty concentrating, migraine headaches, extreme muscle weakness and tremors and paralysis of a limb. If one or more of these symptoms develop, especially after suffering mosquito bites within the previous two weeks, a healthcare provider should be contacted. Persons over the age of 50 are at greatest risk of developing severe neurologic disease from WNV. Some of the neurological effects of WNV may be permanent.

Here are some precautions to take against mosquito bites :

  • Use an insect repellent containing DEET on exposed skin and clothing when you go outdoors, particularly if you are outside between dusk and dawn when mosquitoes are more likely to bite. Insect repellent with permethrin should be used on clothing only.
  • Repair or install window and door screens.
  • Prevent items such as buckets, cans, pool covers, flowerpots, and tires from holding standing water so mosquitoes don’t have a place to breed.
  • Empty your pet’s outdoor water bowl and refill daily.
  • Clean leaves and debris from rain gutters regularly to ensure they are not clogged.

For more information, visit www.ok.gov/health