WEST NILE VIRUS

I. Basic information

1. A flavivirus
2. Related to Japanese encephalitis and St. Louis encephailitis
3. Can affect humans, horses, birds, and other vertebrates
4. Transmitted to humans through mosquito bites (various species); no known cases of person-to-person transmission among humans or between humans and non-mosquito species as of 2005, except through blood transfusions, transplacentally, or through breastfeeding

III. Clinical features

1. Incubation period 3-14d; sx usually last 3-6d
2. Clinical presentation is indistinguishable from other viral encephalitides
3. Most cases are mild or asympomatic
4. "West Nile Fever"--About 20% of cases; sx include fever, malaise, anorexia, n/v, eye pain, HA, myalgias, rash, and lymphadenopathy
5. Neurologic involvement seen in about .7% of cases:
   1. Encephalitis
   2. Meningitis
   3. Acute flaccid paralysis