The Zika Virus Epidemic in Brazil: From Discovery to Future Implications

Abstract

The first confirmed case of Zika virus infection in the Americas was reported in Northeast Brazil in May 2015, although phylogenetic studies indicate virus introduction as early as 2013. Zika rapidly spread across Brazil and to more than 50 other countries and territories on the American continent. The Aedes aegypti mosquito is thought to be the principal vector responsible for the widespread transmission of the virus. However, sexual transmission has also been reported. The explosively emerging epidemic has had diverse impacts on population health, coinciding with cases of Guillain–Barré Syndrome and an unexpected epidemic of newborns with microcephaly and other neurological impairments. This led to Brazil declaring a national public health emergency in November 2015, followed by a similar decision by the World Health Organization three months later. While dengue virus serotypes took several decades to spread across Brazil, the Zika virus epidemic diffused within months, extending beyond the area of permanent dengue transmission, which is bound by a climatic barrier in the south and low population density areas in the north. This rapid spread was probably due to a combination of factors, including a massive susceptible population, climatic conditions conducive for the mosquito vector, alternative non-vector transmission, and a highly mobile population. The epidemic has since subsided, but many unanswered questions remain. In this article, we provide an overview of the discovery of Zika virus in Brazil, including its emergence and spread, epidemiological surveillance, vector and non-vector transmission routes, clinical complications, and socio-economic impacts. We discuss gaps in the knowledge and the challenges ahead to anticipate, prevent, and control emerging and re-emerging epidemics of arboviruses in Brazil and worldwide.

Qu’apprend-t-on de nouveau des épidémies émergentes ?

“…Le génotype qui a diffusé dans le Pacifique a été introduit ultérieurement au Brésil à la faveur de la Coupe de confédérations (juin 2013) avant d'y circuler activement en 2015 puis devenir pandémique en 2016. L'épidémie du Brésil fut déclarée USPPI et a permis de retenir le caractère causal du Zika dans la pathogenèse des microcéphalies primitives et des autres malformations congénitales cérébrales, ainsi que son rôle dans celle du syndrome de Guillain-Barré [56][57][58][59]. S'agissant de l'infection par le virus Zika, la conséquence individuelle de la transmission sexuelle chez une femme enceinte ou en âge de procréation reste la même que la transmission vectorielle opérant en contexte d'expansion épidémique.…”

Congenital Zika syndrome and neuroimaging findings

“…Although previous ZIKV outbreaks occurred in Micronesia in 2007 and in French Polynesia in the 2013-2014 period, the association between congenital ZIKV infection and CNS malformations was recognized only in October 2015, when there was a dramatic increase in the number of cases of microcephaly in northeastern Brazil (1,3-5,8,9) . In February 2016, the World Health Organization declared the relationship between ZIKV infection and congenital malformations an international health emergency (9) .…”

“…In February 2016, the World Health Organization declared the relationship between ZIKV infection and congenital malformations an international health emergency (9) .…”

“…Within Latin America, Brazil was the country most affected by the ZIKV epidemic, approximately 1,500,000 cases being reported between 2015 and 2016, during which time the incidence of microcephaly increased by approximately 20 times in comparison with previous years (1,8,9) . The number of reported cases of ZIKV infection in Brazil has subsequently decreased, from approximately 205,000 cases in 2016 to approximately 13,000 cases in 2017, population immunity being considered the main reason for this decline (9) .…”

“…The number of reported cases of ZIKV infection in Brazil has subsequently decreased, from approximately 205,000 cases in 2016 to approximately 13,000 cases in 2017, population immunity being considered the main reason for this decline (9) . However, the continuous transmission, in Brazil and in the Americas at large, of the four dengue serotypes in recent decades suggests that ZIKV will continue to circulate, making it necessary for physicians to suspect ZIKV infection when there is a clinical profile consistent with the diagnosis (9) .…”