West Nile Virus (WNV)

West Nile virus (WNV) is a virus that is spread to people by the bite of an infected mosquito. Symptoms generally appear three to 15 days after being bitten. People with weakened immune systems and people over the age of 50 are at greatest risk for developing complications or illness from the virus. Currently, no vaccine against WNV is available for people.

Page updated on Mar 29, 2017 at 2:56 PM

West Nile Virus in Alexandria 

West Nile can be found in mosquitoes beginning in July or very early August. 

Transmission Cycle  

West Nile Virus is passed regularly between birds and mosquitoes.

  • An infected bird is bitten by a mosquito
  • The mosquito picks up the virus from the bird
  • The infected mosquito feeds on an uninfected bird; the virus is passed to the bird and the WNV cycle continues.
  • Sometimes, the infected mosquito will feed on humans or horses. Some of these humans and horses can get sick or die from the infection.

WNV Transmission Cycle, Courtesy of the CDC  

Signs and Symptoms 

Symptoms usually appear three to fifteen days after a person is bitten by an infected mosquito. Approximately 80% of people who are infected with WNV will not feel sick.

Mild symptoms: Up to 20% of the people infected with WNV develop WNV fever. Symptoms may include fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach, and/or back. Symptoms may last for a few days to several weeks.

Serious symptoms: About one in 150 people develop severe illness. This may include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, or paralysis. These symptoms may last several weeks and neurological effects may be permanent. West Nile virus infection can be fatal.

Contact Us

Vector-Borne Illness Prevention Program 
Alexandria Health Department   
4480 King Street, 3rd Floor 
Alexandria, VA 22302

Phone: 703.746.4910 
Hours: 8 a.m. to 4:30 p.m. (M,Tu,W,F) and 1:30 p.m. to 4:30 p.m. (Th)