Global emergence of West Nile virus: Threat & preparedness in special perspective to India

Abstract

West Nile virus (WNV) is a mosquito-borne single-stranded RNA neurotropic virus within the family Flaviviridae. The virus was first reported in the West Nile province of Uganda in 1937. Since then, sporadic cases have been reported until the last two decades when it has emerged as a threat to public health. The emergence of WNV with more severity in recent times is intriguing. Considering this phenomenon, the WNV-affected areas of the world were distinguished as old versus new in a depicted world map. The present review showcases the historical and epidemiological perspectives of the virus, genetic diversity of prevailing lineages and clinical spectrum associated with its infection. Emergence of the virus has been discussed in special context to India because of co-circulation of different WNV lineages/strains along with other flaviviruses. Recent laboratory diagnostics, vaccine development and clinical management associated with WNV infection have also been discussed. Further, the research gaps, especially in context to India have been highlighted that may have a pivotal role in combating the spread of WNV.

Keywords: Clinical management; West Nile virus; epidemiology; laboratory diagnostic; public health; vaccines.

Fig. 1

Schematic world maps: (A) showing distribution of West Nile virus lineages, (B) showing areas with West Nile virus human serological evidence. Data searches were undertaken using online references of the literature site, PubMed (http://www.ncbi.nlm.nih.gov/sites/entrez), supplemented with additional data archives of Centre for Disease Control, (https://www.cdc.gov/westnile/statsmaps/index.html); World Health Organization (http://www.who.int/news-room/fact-sheets/detail/west-nile-virus); European Centre for Disease Prevention and Control (https://ecdc.europa.eu/en/west-nile-fever/surveillance-and-disease-data/disease-data-ecdc). The maps were prepared using GIS software, ArcGIS 10.2 (Redlands, CA, USA). The source of outline map is a web portal (https://www.diva-gis.org/).

Fig. 2

Schematic map of India showing distribution of West Nile virus lineages and West Nile virus human serological evidence. Data searches were undertaken using online references of the literature site, PubMed (http://www.ncbi.nlm.nih.gov/sites/entrez). The source of outline map is a web portal (https://www.diva-gis.org/).

Fig. 3

Molecular phylogenetic analysis of West Nile virus lineages by Maximum Likelihood method (timetree): The tree was generated using the RelTime method. Relative divergence times for all branching points in the topology were calculated based on the General Time Reversible model. A discrete Gamma distribution was used to model evolutionary rate differences among sites [5 categories (+G, parameter=1.8515)]. The rate variation model allowed for some sites to be evolutionarily invariable [(+I), 7.0510% sites]. The tree is drawn to scale, with branch lengths measured in the relative number of substitutions per site. Evolutionary analyses were conducted in MEGA6 (Pennsylvania State University, PA, USA) with JEV strain GP-78 as an outgroup.