West Nile virus. Primer for family physicians.

OBJECTIVE: To provide primary care physicians with an understanding of West Nile virus in North America. This article focuses on epidemiology, clinical features, diagnosis, and prevention of infection.

QUALITY OF EVIDENCE: MEDLINE and EMBASE searches revealed epidemiologic, surveillance, cohort, and outcome studies providing level II evidence. There were no randomized controlled trials of treatment. Recommended prevention and treatment strategies are based on level II and III evidence.

MAIN MESSAGE: The mosquito-borne virus that first appeared on this continent in 1999 is now prevalent throughout North America. Most infections are asymptomatic. Fewer than 1% of those infected develop severe illness; 3% to 15% of those with severe illness die. While methods for controlling the mosquito population are available, we lack evidence that they reduce infection in the general human population. Family physicians have an important role in advising their patients on ways to prevent infection and in identifying patients who might be infected with West Nile virus.

CONCLUSION: The general population is at low risk of West Nile virus infection. Prevention of infection rests on controlling the mosquito population and educating people on how to protect themselves against mosquito bites.