Yellow fever in the Americas: the growing concern about new epidemics [version 1; referees: 1 approved, 1 approved with reservations]

Yellow fever (YF) is a haemorrhagic viral disease with a high case fatality rate. It is considered a reemerging infectious disease of remarkable importance. During the last outbreaks in Angola (2015-2016) and Brazil (2016-2017), many cases of YF emerged despite high YF vaccination coverage, increasing the risk of major epidemics in the Americas. Several factors, including the vast border and migratory status of Brazil, the widespread distribution of Aedes mosquitoes and the lack of efficient health policies and surveillance systems, favour this complex epidemiological scenario of reemergence. Therefore, mass vaccination of the population at risk, public health awareness and preparedness are urgently needed in this region. This article describes the current global epidemiological situation of YF, focusing especially on the Americas, as well the risk and vulnerabilities in the region that would be of concern for major expansion to other countries apart from Brazil.