West Nile Virus Surveillance

West Nile virus (WNV) is an arthropod-borne virus (arbovirus) most commonly spread by infected mosquitoes that can lead to severe fever, encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord).  The primary vector in Ohio is the northern house mosquito, Culex pipiens.  Mosquitoes become infected when they feed on infected birds.  Infected mosquitoes can then spread the virus to humans and other animals when they bite.

Approximately 80 percent of people who are infected with WNV will not show any symptoms at all, but there is no way to know in advance if you will develop an illness or not.  Those who do develop symptoms usually do so between three to 14 days after they are bitten by the infected mosquito:

  • Serious symptoms in a few people.  About one in 150 people infected with WNV will develop severe illness.  The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.  These symptoms may last several weeks, and neurological effects may be permanent.
  • Milder symptoms in some people.  Up to 20 percent of people who become infected will have symptoms that can include fever, headache, body aches, nausea, vomiting and sometimes swollen lymph glands or a skin rash on the chest, stomach and back.  Symptoms can last for a few days to as long as several weeks.

There is no specific treatment for WNV infection, and care is based on symptoms.

Ways to reduce the chance of exposure to mosquitoes include reducing water-holding areas around your home that provide breeding habitats for mosquitoes, using insect repellant containing DEET on exposed skin (especially during early morning hours and early evening hours), or covering exposed skin with clothing. To download a copy of an informational brochure on West Nile Virus and other mosquito borne diseases click here: Mosquito Brochure