West Nile Virus Surveillance Program
Health Care Professionals
- First isolated in 1937 in Uganda from blood of a febrile woman.
- Family: Flaviviridae
- Genus: Flavivirus
- Japanese Encephalitis Antigenic Complex
- Complex includes: Alfuy, Japanese encephalitis, Kokobera, Koutango, Kunjin, Murray Valley encephalitis, St. Louis encephalitis, Stratford, Usutu, and West Nile viruses.
- All are transmissible by mosquitoes, many can cause febrile, sometimes fatal, illnesses in humans.
West Nile Fever: Human Disease
- Asymptomatic to mild illness
- Incubation period 5-15 days
- Fever, influenza-like illness with abrupt onset
- Moderate to high fever
- Headache, sore throat, backache, myalgia, arthralgia, fatigue, vomiting, conjunctivitis
- Rash, lymphadenopathy
- Acute aseptic meningitis or encephalitis
- Most fatal cases >50 years old.
Health Risks for Humans
- Birds are more likely to be infected than humans.
- Birds are more likely than humans to be ill.
- Most mosquitoes are not infected with WN.
- In northern areas the highest risk of virus transmission in humans is in Aug and Sept.
- Most people infected do not become ill.
- Older and immuno-compromised are at greater risk of becoming seriously ill.
- Children are not in a higher risk group.