[Primary infection with West-Nile virus].

BACKGROUND: The recent outbreak of an epidemic of West-Nile fever in New-York revealed this virus' responsibility in some cases of fatal encephalitis. However the clinical manifestations of the infection may be mild as in the case reported herein. CASE-REPORT: A 41-year-old woman without previous medical history presented an acute febrile rash after a trip to Senegal. The course was spontaneously favorable after 5 days, with a biphasic fever at day 3. Reverse passive hemagglutination test confirmed the diagnosis of acute West-Nile fever. DISCUSSION: West-Nile virus, a mosquito-borne flavivirus is usually responsible for a flue-like disease presenting a maculopapular rash in half of the cases. The biphasic evolution of fever is suggestive of the diagnosis. The diagnosis relies on serological tests but cross-reactivities with heterologous flaviviruses may render the interpretation difficult. A rapid recovery is usual but fatal meningoencephalitis can occur especially in the elderly. Treatment is supportive and prevention is limitation of human exposure. West-Nile virus is widely distributed (Africa, Asia, Middle East), but is also endemic in european areas and responsible for seasonal infections.