Epidemiology
Caused by West Nile Virus (WNV) and transmitted to humans by bite of mosquitoes (primarily Culex sp).
The virus is found across the continental United States. Activity typically occurs during summer months and into the fall.
Though rare, the virus may be transmitted from person-to-person through blood transfusion, organ transplantation, and perinatally during pregnancy, delivery, or breastfeeding.
Symptoms and Presentation
Most infected people are asymptomatic. Approximately 20% develop a fever that may be accompanied by headaches, myalgia, arthralgia, diarrhea, or rash. <1% develop encephalitis or meningitis.
Testing and Diagnosis
WNV is diagnosed by presence of immunoglobulin M antibody (IgM) in the serum using enzyme -linked immunosorbent assay (ELISA). Approximately 75% of cases will be positive within 1-4 days; virtually 100% are positive by 7-8 days. The presence of IgM in cerebrospinal fluid is diagnostic of neuroinvasive infection.
Additionally, a complete blood count may demonstrate mild lymphocytopenia and anemia.
Treatment
There is no effective antiviral treatment for West Nile virus.
Management focuses on supportive care (rest, fluid, and over the counter pain medications). Severe symptoms may require hospitalization.
Resources
Learn more about mosquito-borne illnesses
