Abstract
Yellow fever (YF) is an acute viral disease, affecting humans and non-human primates (NHP), caused by the yellow fever virus (YFV). Despite the existence of a safe vaccine, YF continues to cause morbidity and mortality in thousands of people in Africa and South America. Since 2016, massive YF outbreaks have taken place in Brazil, reaching YF–free zones, causing thousands of deaths of humans and NHP. Here we reviewed the main epidemiological aspects, new clinical findings in humans, and issues regarding YFV infection in vectors and NHP in Brazil. The 2016–2019 YF epidemics have been considered the most significant outbreaks of the last 70 years in the country, and the number of human cases was 2.8 times higher than total cases in the previous 36 years. A new YFV lineage was associated with the recent outbreaks, with persistent circulation in Southeast Brazil until 2019. Due to the high number of infected patients, it was possible to evaluate severity and death predictors and new clinical features of YF. Haemagogus janthinomys and Haemagogus leucocelaenus were considered the primary vectors during the outbreaks, and no human case suggested the occurrence of the urban transmission cycle. YFV was detected in a variety of NHP specimens presenting viscerotropic disease, similar to that described experimentally. Further studies regarding NHP sensitivity to YFV, YF pathogenesis, and the duration of the immune response in NHP could contribute to YF surveillance, control, and future strategies for NHP conservation.
Highlights
The virus and transmission cycle Yellow fever virus (YFV) is the prototype member of the genus Flavivirus, with a single-strand positive-sense RNA genome of approximately 11 kb [11]
Given the ongoing yellow fever (YF) outbreaks in Brazil (2016–2019), we present the main aspects of sylvatic YF, including historical and recent outbreaks in the country
A new YFV lineage was associated with the 2016–2019 outbreaks
Summary
Yellow fever virus (YFV) causes yellow fever (YF), an acute disease affecting humans and non-human primates (NHP) in several South American and African countries [1, 2]. YF ranges from asymptomatic infection to non-specific symptomatic illness and fatal hemorrhagic fever [1, 2]. Humans are considered incidental hosts for YFV. The virus is maintained by different cycles in tropical and subtropical regions of sub-Saharan Africa and South America via transmission among different mosquitoes and NHP [2, 7–9]. Neotropical NHP are considered highly susceptible to YFV infection [10], which may be related to the recent introduction of the virus into the Americas [7]. Given the ongoing YF outbreaks in Brazil (2016–2019), we present the main aspects of sylvatic YF, including historical and recent outbreaks in the country
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