West Nile virus. Update for family physicians.

OBJECTIVE To review the epidemiology and disease manifestations of West Nile virus (WNV) in North America and to describe the current status of therapeutic approaches and vaccines for treating or preventing viral illness.

QUALITY OF EVIDENCE Since 1999, research initiatives investigating the ecology, epidemiology, and biology of WNV have increased substantially. These studies provide a foundation for understanding current activity and predicting future activity and for describing the effect of WNV on human health.

MAIN MESSAGE West Nile virus is transmitted to humans primarily through bites from infected mosquitoes. Most people infected have no symptoms; a few have clinical manifestations ranging from febrile illness to neurologic syndromes and possibly death. Risk of serious disease increases with age, and substantial long-term morbidity has been observed in patients who develop severe neurologic illness. No specific antiviral therapy or vaccine currently exists.

CONCLUSION West Nile virus has established itself in North America and has become an important public health concern. Decreasing risk of virus-associated illness requires seasonal preventive and control measures.