Molecular Evolution of Zika Virus during Its Emergence in the 20th Century

TLDR

Zika virus, a mosquito‑borne flavivirus first isolated in Uganda in 1947, has been enzootic across Africa and Asia with sporadic human cases until a 2007 Micronesia outbreak, periodic circulation reported in West Africa since 1968, yet the genetic relationships among West African strains remain poorly understood. The study aimed to assess ZIKV spread and molecular epidemiology by analyzing 37 isolates from 1968‑2002 in Senegal and Côte d'Ivoire. The authors examined 37 isolates from Senegal and Côte d'Ivoire, supplemented with strains from six additional countries. The results indicate at least two independent introductions of ZIKV into West Africa during the 20th century, with lineages not restricted by mosquito vector species, evidence of natural recombination, and a loss of the N154 glycosylation site in the envelope protein possibly adapting to *Aedes dalzieli*.

Abstract

Zika virus (ZIKV) is a mosquito-borne flavivirus first isolated in Uganda in 1947. Although entomological and virologic surveillance have reported ZIKV enzootic activity in diverse countries of Africa and Asia, few human cases were reported until 2007, when a Zika fever epidemic took place in Micronesia. In the context of West Africa, the WHO Collaborating Centre for Arboviruses and Hemorrhagic Fever at Institut Pasteur of Dakar (http://www.pasteur.fr/recherche/banques/CRORA/) reports the periodic circulation of ZIKV since 1968. Despite several reports on ZIKV, the genetic relationships among viral strains from West Africa remain poorly understood. To evaluate the viral spread and its molecular epidemiology, we investigated 37 ZIKV isolates collected from 1968 to 2002 in six localities in Senegal and Côte d'Ivoire. In addition, we included strains from six other countries. Our results suggested that these two countries in West Africa experienced at least two independent introductions of ZIKV during the 20(th) century, and that apparently these viral lineages were not restricted by mosquito vector species. Moreover, we present evidence that ZIKV has possibly undergone recombination in nature and that a loss of the N154 glycosylation site in the envelope protein was a possible adaptive response to the Aedes dalzieli vector.