Zika fever and congenital Zika syndrome: An unexpected emerging arboviral disease

Abstract

Unlike its mosquito-borne relatives, such as dengue, West Nile, and Japanese encephalitis viruses, which can cause severe human diseases, Zika virus (ZIKV) has emerged from obscurity by its association with a suspected "congenital Zika syndrome", while causing asymptomatic or mild exanthematous febrile infections which are dengue- or rubella-like in infected individuals. Despite having been discovered in Uganda for almost 60 years, <20 human cases were reported before 2007. The massive epidemics in the Pacific islands associated with the ZIKV Asian lineage in 2007 and 2013 were followed by explosive outbreaks in Latin America in 2015. Although increased mosquito breeding associated with the El Niño effect superimposed on global warming is suspected, genetic changes in its RNA virus genome may have led to better adaptation to mosquitoes, other animal reservoirs, and human. We reviewed the epidemiology, clinical manifestation, virology, pathogenesis, laboratory diagnosis, management, and prevention of this emerging infection. Laboratory diagnosis can be confounded by cross-reactivity with other circulating flaviviruses. Besides mosquito bite and transplacental transmission, the risk of other potential routes of transmission by transfusion, transplantation, sexual activity, breastfeeding, respiratory droplet, and animal bite is discussed. Epidemic control requires adequate clearance of mosquito breeding grounds, personal protection against mosquito bite, and hopefully a safe and effective vaccine.

Keywords: Aedes; Arbovirus; Flavivirus; Microcephaly; Mosquito; Virus; Zika.

Figure 1

Phylogenetic tree of selected ZIKV strains with partial nucleotide sequences of Envelope gene. The tree was constructed by the maximum likelihood method using PhyML with automatic model selection by SMS (beta version, online execution http://www.atgc-montpellier.fr/phyml-sms/). The best model in each tree was calculated and selected automatically. aLRT was applied and only those branches with over 75% aLRT values are shown in the trees. Viruses are labelled as follow: virus name/strain/accession number/host/location/region/year. DENV1, Dengue virus 1; JEV, Japanese encephalitis virus; SPOV, Spondweni virus; TBEV, tick-borne encephalitis virus; WNV, West Nile virus; YFV, Yellow fever virus; ZIKV, Zika virus.