Abstract
The recent resurgence of yellow fever virus (YFV) activity in the tropical regions of Africa and South America has sparked renewed interest in this infamous arboviral disease. Yellow fever virus had been a human plague for centuries prior to the identification of its urban transmission vector, the Aedes (Stegomyia) aegypti (Linnaeus) mosquito species, and the development of an efficient live-attenuated vaccine, the YF-17D strain. The combination of vector-control measures and vaccination campaigns drastically reduced YFV incidence in humans on many occasions, but the virus never ceased to circulate in the forest, through its sylvatic invertebrate vector(s) and vertebrate host(s). Outbreaks recently reported in Central Africa (2015–2016) and Brazil (since late 2016), reached considerable proportions in terms of spatial distribution and total numbers of cases, with multiple exports, including to China. In turn, questions about the likeliness of occurrence of large urban YFV outbreaks in the Americas or of a successful import of YFV to Asia are currently resurfacing. This two-part review describes the current state of knowledge and gaps regarding the molecular biology and transmission dynamics of YFV, along with an overview of the tools that can be used to manage the disease at individual, local and global levels.
Highlights
The recent resurgence of yellow fever virus (YFV) activity in the tropical regions of Africa and South America has sparked renewed interest in this infamous arboviral disease
Yellow fever virus (YFV) is the type species of the genus Flavivirus, owing its name to the jaundice associated with the liver dysfunction characteristic of clinically apparent human yellow fever
They were subsequently followed by the Yucatan epidemic (Cogolludo 1648) which was recorded more than a century before the first report of an African yellow fever (YF) epidemic in 1778 [7], that occurred among the British troops at St
Summary
Yellow fever virus is endemic in the tropical regions of sub-Saharan Africa and South-America, where its natural circulation is conditioned by the presence of both its mosquito vectors and primate hosts. Referred to as the “Zone of emergence”, small-scale outbreaks (sylvatic/savannah cycles) can locally involve peridomestic “bridge” mosquito vectors from the genus Aedes [47,48,49] Such intermediates cycles may settle when (i) humans get infected in the forest through the bite of a sylvatic mosquito and bring back the virus into their village where secondary transmission is ensured by peridomestic mosquito populations; (ii) the virus is introduced into plantations by viraemic monkeys on which peridomestic mosquito populations may feed. In Africa, the main sylvatic vector is Aedes (Stegomyia) africanus (Theobald) while at the fringe of forested areas several other Aedes species may contribute to the intermediate sylvatic/savannah cycles, which involve both human and non-human primates. These may occasionally participate in the sylvatic cycle. Green dots correspond to case reports from locations smaller than 5 × 5 km in area, a blue shade to case reports from locations over 5 × 5 km in area and a pale green shade, to contemporary risk zones as defined by Jentes and colleagues [63]
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