Re-emergence of yellow fever in the neotropics — quo vadis?

Abstract

Yellow fever virus (YFV) is the etiological agent of yellow fever (YF), an acute hemorrhagic vector-borne disease with a significant impact on public health, is endemic across tropical regions in Africa and South America. The virus is maintained in two ecologically and evolutionary distinct transmission cycles: an enzootic, sylvatic cycle, where the virus circulates between arboreal Aedes species mosquitoes and non-human primates, and a human or urban cycle, between humans and anthropophilic Aedes aegypti mosquitoes. While the urban transmission cycle has been eradicated by a highly efficacious licensed vaccine, the enzootic transmission cycle is not amenable to control interventions, leading to recurrent epizootics and spillover outbreaks into human populations. The nature of YF transmission dynamics is multifactorial and encompasses a complex system of biotic, abiotic, and anthropogenic factors rendering predictions of emergence highly speculative. The recent outbreaks in Africa and Brazil clearly remind us of the significant impact YF emergence events pose on human and animal health. The magnitude of the Brazilian outbreak and spillover in densely populated areas outside the recommended vaccination coverage areas raised the specter of human — to — human transmission and re-establishment of enzootic cycles outside the Amazon basin. Herein, we review the factors that influence the re-emergence potential of YFV in the neotropics and offer insights for a constellation of coordinated approaches to better predict and control future YF emergence events.

Real-Time Genomic Surveillance during the 2021 Re-Emergence of the Yellow Fever Virus in Rio Grande do Sul State, Brazil

“…This probably interferes with the speed and even the direction of viral spread. Noteworthy, the YFV expansion wave (2014–2021) revealed the suitability of climate and ecological conditions for the occurrence of YFV outbreaks in several Brazilian regions [ 4 , 45 , 46 , 47 ]. Such spreading events included even the three southernmost states of Brazil (Paraná, Santa Catarina, and Rio Grande do Sul), with a subtropical temperate climate and great losses of forest areas, through which viral circulation could more easily occur [ 48 ].…”

Real-time genomic surveillance during the 2021 re-emergence of the yellow fever virus in Rio Grande do Sul State, Brazil

“…Epidemic outbreaks in the sylvatic cycle of YFV demands a high density of competent vectors and susceptible NHP's presence, acting as an amplifier for the virus (Abreu et al, 2019b;Cardoso et al, 2010;Mares-Guia et al, 2020;Pinheiro et al, 2019). Importantly, the YFV expansion wave (2014-2021) revealed the suitability of climate and ecological conditions for the occurrence of YFV outbreaks in several Brazilian regions, even though in the three southernmost states of Brazil (Paraná, Santa Catarina and RS), which have a subtropical temperate climate and great loss of forest areas, through which viral circulation can occur (Abreu et al, 2019a;Delatorre et al, 2019;Sacchetto et al, 2020a;Sacchetto et al, 2020b;Rosa et al, 2021). Therefore, it is important to strengthen surveillance.…”

Microclimate and the vertical stratification of potential bridge vectors of mosquito‑borne viruses captured by nets and ovitraps in a central Amazonian forest bordering Manaus, Brazil

“…Arboreal mosquitoes transmit sylvatic arthropod-borne viruses (arboviruses), such as yellow fever virus (YFV, Flaviviridae : Flavivirus ), among wildlife in forests in Africa and Latin America 1 . YFV was first introduced to the Americas in the seventeenth century 2 , transported by Aedes aegypti mosquitoes among shipments of enslaved people from West Africa 3 . Having arrived in the neotropics, the virus caused devastating urban outbreaks and eventually spilled back into a sylvatic cycle involving susceptible monkeys and Haemagogus and Sabethes species mosquitoes 1 , 2 .…”