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Zika puzzle in Brazil: peculiar conditions of viral introduction and dissemination - A Review
Possas, Cristina; Brasil, Patricia; Marzochi, Mauro CA; Tanuri, Amilcar; Martins, Reinaldo M; Marques, Ernesto TA; Bonaldo, Myrna C; Ferreira, Antonio GP; Lourenço-de-Oliveira, Ricardo; Nogueira, Rita Maria R; Sequeira, Patricia C; Marzochi, Keyla BF & Homma, Akira
Abstract
This article discusses the peculiar conditions that favoured the unexpected introduction of Zika virus into the poorest
northeastern region of Brazil in 2015, its speed of transmission to other Brazilian states, other Latin American
countries and other regions, and the severity of related neurological disorders in newborns and adults. Contrasting with
evidence that Zika had so far caused only mild cases in humans in the last six decades, the epidemiological scenario of
this outbreak in Brazil indicates dramatic health effects: in 2015, an increase of 20-fold in notified cases of microcephaly
and/or central nervous system (CNS) alterations suggestive of Zika congenital infection, followed by an exponential
increase in 2016, with 2366 cumulative cases confirmed in the country by the end of December 2016. A significant
increase in Guillain-Barré syndrome in adults has also been reported. Factors involved in viral dissemination, neural
pathogenesis and routes of transmission in Brazil are examined, such as the role of social and environmental factors and
the controversies involved in the hypothesis of antibody-dependent enhancement, to explain the incidence of congenital
Zika syndrome in Brazil. Responses to the Zika outbreak and the development of new products are also discussed.
Keywords
Zika; microcephaly; congenital Zika syndrome; neurological disorders; pathogenesis; epidemiology
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