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Update on Yellow Fever

Yellow fever is an acute viral hemorrhagic fever transmitted by certain species of mosquitoes of the genera Aedes and Haemogogus. The yellow fever virus belongs to the genus Flavivirus. Since January 2017, an outbreak of yellow fever has been raging in several states of Brazil. Transmission of the yellow fever virus continues to spread across the country, and the situation is being closely monitored by the World Health Organization (WHO) and the European Centre for Disease Prevention and Control (ECDC), which are providing regular updates. Between January 6 and May 4, 2017, a total of 1,392 cases were reported (half of which (n=729, 52%) were confirmed cases). Yellow fever can be prevented with a single-dose vaccine, which provides long-lasting immunity within 10 days of vaccination. For the record, the yellow fever vaccine is mandatory for travel to certain countries or territories (including the department of French Guiana).Yellow fever is difficult to diagnose. It can be confused with severe malaria, leptospirosis, viral hepatitis (especially fulminant forms), other hemorrhagic fevers, other flavivirus diseases (such as dengue hemorrhagic fever), or poisoning. Diagnosis is clinical and laboratory-based (figure) and must be confirmed by the National Reference Center (NRC) for Arboviruses. In France, yellow fever is a notifiable disease. Current procedures require reporting of suspected cases to the Regional Health Agency by any appropriate means (contact information on page 4) even before confirmation by the NRC, followed by notification after laboratory confirmation.The case definition used is a clinical presentation suggestive of yellow fever in a person arriving from an endemic area. Only cases confirmed by the NRC for Arboviruses in mainland France or by the NRC for Arboviruses and Influenzae Viruses in the Antilles-Guyana region are reported. Confirmation is also required for international reporting.