Zika puzzle in Brazil: peculiar conditions of viral introduction and dissemination - A Review

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

Arboviruses emerging in Brazil: challenges for clinic and implications for public health

Arboviruses have been emerging in different parts of the world due to genetic changes in the virus, alteration of the host and vector population dynamics, or because of anthropogenic environmental factors. These viruses’ capacity for adaptation is notable, as well as the likelihood of their emergence and establishment in new geographic areas. In Brazilian epidemiologic scenario, the most common arboviruses are DENV, CHIKV, and ZIKV, although others may spread in the country. Little is yet known of the impact of viral co-circulation, which would theoretically result in more intense viremia or other immunological alterations that could trigger autoimmune diseases, such as Guillain-Barré syndrome. The impact on morbidity and mortality intensifies as extensive epidemics lead to a high number of affected individuals, severe cases, and implications for health services, mainly due to the absence of treatment, vaccines, and effective prevention and control measures.Notifica-se a emergência de arboviroses em diferentes regiões do planeta em decorrência de mudanças genéticas no vírus, alteração da dinâmica populacional de hospedeiros e vetores ou por fatores ambientais de origem antropogênica. É notável a capacidade de adaptação desses vírus e a possibilidade de emergirem e se estabelecerem em novas áreas geográficas. No contexto epidemiológico brasileiro, os arbovírus de maior circulação são DENV, CHIKV e ZIKV, embora existam outros com potencial de disseminação no País. O impacto da cocirculação viral ainda é pouco conhecido, a qual teoricamente resultaria em viremias mais intensas ou outras alterações imunológicas que poderiam ser o gatilho para doenças autoimunes, como a síndrome de Guillain-Barré. O impacto na morbidade e mortalidade se intensifica à medida que extensas epidemias pressupõem grande número de indivíduos acometidos, casos graves e implicações sobre os serviços de saúde, principalmente diante da ausência de tratamento, vacinas e medidas efetivas de prevenção e controle