Ecological and environmental factors affecting transmission of sylvatic yellow fever in the 2017-2019 outbreak in the Atlantic Forest, Brazil.

BACKGROUND: Yellow fever virus (YFV) is an arbovirus that, despite the existence of a safe and effective vaccine, continues to cause outbreaks of varying dimensions in the Americas and Africa. Between 2017 and 2019, Brazil registered un unprecedented sylvatic YFV outbreak whose severity was the result of its spread into zones of the Atlantic Forest with no signals of viral circulation for nearly 80 years. METHODS: To investigate the influence of climatic, environmental, and ecological factors governing the dispersion and force of infection of YFV in a naïve area such as the landscape mosaic of Rio de Janeiro (RJ), we combined the analyses of a large set of data including entomological sampling performed before and during the 2017-2019 outbreak, with the geolocation of human and nonhuman primates (NHP) and mosquito infections. RESULTS: A greater abundance of Haemagogus mosquitoes combined with lower richness and diversity of mosquito fauna increased the probability of finding a YFV-infected mosquito. Furthermore, the analysis of functional traits showed that certain functional groups, composed mainly of Aedini mosquitoes which includes Aedes and Haemagogus mosquitoes, are also more representative in areas where infected mosquitoes were found. Human and NHP infections were more common in two types of landscapes: large and continuous forest, capable of harboring many YFV hosts, and patches of small forest fragments, where environmental imbalance can lead to a greater density of the primary vectors and high human exposure. In both, we show that most human infections (~ 62%) occurred within an 11-km radius of the finding of an infected NHP, which is in line with the flight range of the primary vectors. CONCLUSIONS: Together, our data suggest that entomological data and landscape composition analyses may help to predict areas permissive to yellow fever outbreaks, allowing protective measures to be taken to avoid human cases.

Taxonomic history of species without subgeneric placement in the genus Wyeomyia Theobald (Diptera: Culicidae) and recognition of Wy. compta Senevet amp; Abonnenc as a junior synonym of Wy. argenteorostris (Bonne-Wepster amp; Bonne).

The mosquito genus Wyeomyia (Diptera: Culicidae) includes 17 subgenera and 140 species, 30 of which are without subgeneric placement. The taxonomic history of the unplaced species is summarized and the validity of Wy. compta Senevet Abonnenc is discussed based on examination of the type material. It is clear that the description of Wy. compta was based on specimens belonging to two different species. The holotype adult female is identical to Wy. argenteorostris (Bonne-Wepster Bonne) whereas the characters described from a larval exuviae mounted on the same slide with the holotype of Wy. albocaerulea Senevet Abonnenc coincide with those which characterize the subgenus Dodecamyia. Since the larval exuviae cannot be definitely associated with the holotype female and it belongs to either Wy. aphobema Dyar or another species of the subgenus Dodecamyia, it cannot be afforded type status. Therefore, Wy. compta is synonymized with Wy. argenteorostris.