West Nile Virus


Fight the Bite- Avoid mosquitoes!

West Nile Fever in Humans

Most WNV infections are mild and often clinically unapparent. Approximately 20% of those infected develop a generally mild illness. The incubation period is thought to range from 3 to 14 days. Symptoms generally last 3 to 6 days.

How to protect yourself

  • Avoid spending time outside when mosquitoes are most active.
  • When outdoors, wear long pants and long sleeves when appropriate.
  • Apply DEET insect repellent according to instructions.
  • Repair or replace damaged screens around windows – insure tight fitting.
  • Remove all sources of standing water.
  • Report heavy mosquito populations to Vector Control.

Symptoms of West Nile Fever-Humans

Reports from earlier outbreaks describe the mild form of WNV infection as a febrile illness of sudden onset often accompanied by:

  • malaise headache
  • anorexia myalgia
  • nausea rash
  • vomiting lymphadenopathy
  • eye pain

Advanced Age Groups: The most significant risk factor for developing severe neurological disease is advanced age. Encephalitis is more commonly reported than meningitis. Approximately 1 in 150 infections will result in severe neurological disease.

Rash: A minority of patients with severe disease developed a maculopapular or morbilliform rash involving the neck, trunk, arms, or legs.

Musculoskeletal: Several patients have experienced severe muscle weakness and flaccid paralysis.

Transmission Cycle

How Mosquitoes Are Infected How Birds get West Nile Virus
  • Feeding on viremic host
  • Amount of virus in the blood
  • Birds infect mosquitoes
  • Humans & horses do not infect mosquitoes
  • Vertical Transmission
  • Species differences
  • Bite of infected mosquito
  • Bite of infected soft tick (Russia)
  • Bird-to bird transmission shown experimentally
  • Oral transmission

Report Dead Birds