Transmission of West Nile Virus

Transmission of the Virus

Per the Center for Disease Control and Prevention, West Nile Virus is most commonly transmitted to humans by mosquitoes.

Additional routes of human infection have also been documented. It is important to note that these methods of transmission represent a very small portion of cases. These methods include:

  • Blood transfusions
  • Organ transplants
  • Exposure in a laboratory setting
  • From mother to baby during pregnancy, delivery, or breastfeeding

West Nile Virus is not transmitted:

  • From person-to-person or from animal-to-person through casual contact. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have this or any viral infection.
  • From handling live or dead infected birds. You should avoid bare-handed contact when handling any dead animal. If you are disposing of a dead bird, use gloves or double plastic bags to place the carcass in a garbage can.
  • Through consuming infected birds or animals. In keeping with overall public health practice, and due to the risk of known food-borne pathogens, always follow procedures for fully cooking meat from either birds or mammals.

Transmission Cycle

According to the National Institute of Allergy and Infectious Diseases:

The first step in the transmission cycle of West Nile virus (WNV) happens when a mosquito bites an infected bird or animal and gets the virus while feeding on the animal's blood. The infected mosquito can then transmit the virus to another bird or animal when it feeds again.

Crows are highly susceptible to lethal infection, as are robins, blue jays, and other birds. Scientists have identified more than 138 bird species that can be infected and more than 43 mosquito species that can transmit WNV.

Although the virus usually cycles between mosquitoes and birds, infected female mosquitoes also can transmit WNV through their bites to humans and other "incidental hosts," such as horses. With so many susceptible hosts to amplify the virus and so many types of mosquitoes to transmit it, WNV has spread rapidly across the United States.

Remember the 4 D's of West Nile Virus Prevention

  1. Dusk to Dawn
  2. Dress
  3. Drain
  4. DEET