West Nile Virus Surveillance Program

Health Risks for Humans

  • Birds are more likely to be infected than humans;
  • Birds are more likely than humans to become ill
  • Most mosquitoes are not infected;
  • In northern areas the highest risk of virus transmission in humans is in August and September;
  • Most people infected do not become ill;
  • Older and immunocompromised individuals are at greater risk of becoming seriously ill;
  • Most fatal cases occur in people over 50 years old.
  • Children are not in a higher risk group.

West Nile Fever

  • Asymptomatic to mild illness;
  • Incubation period 5-15 days;
  • Moderate to high fever, influenza-like illness with abrupt onset;
  • Headache, sore throat, backache, myalgia, arthralgia, fatigue, vomiting, conjunctivitis;
  • Rash, lymphadenopathy;
  • Acute aseptic meningitis or encephalitis


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