An outbreak of yellow fever occurring in rural Brazil deserves careful attention by world health authorities, notes NIAID Director Anthony S. Fauci, M.D., in the New England Journal of Medicine.Dr. Fauci and his associate Catharine I. Paules, M.D., write that this latest outbreak of a serious mosquito-borne virus comes as Zika virus, which is spread by the same mosquito as yellow fever virus, continues to affect countries throughout the Americas.
Although the outbreak is currently a manifestation of the “sylvatic,” or jungle, transmission cycle, authorities should remain alert to the possibility of it developing into its “urban” cycle, in which city-dwelling mosquitoes spread yellow fever virus directly to people. During an urban cycle of yellow fever in Africa in 2015-16, the world’s emergency vaccine stockpile reserve was exhausted, limiting the number of available vaccine doses and making the outbreak more difficult to control. To prevent a similar occurrence during a future yellow fever outbreak in Brazil or elsewhere, the authors note that “early identification of cases and rapid implementation of public health management and prevention strategies, such as mosquito control and appropriate vaccination, are critical.”