Emerging phleboviruses

Abstract

The Bunyavidae family is the largest grouping of RNA viruses and arguably the most diverse. Bunyaviruses have a truly global distribution and can infect vertebrates, invertebrates and plants. The majority of bunyaviruses are vectored by arthropods and thus have the remarkable capability to replicate in hosts of disparate phylogeny. The family has provided many examples of emerging viruses including Sin Nombre and related viruses responsible for hantavirus cardiopulmonary syndrome in the Americas, first identified in 1993, and Schmallenberg virus which emerged in Europe in 2011, causing foetal malformations in ruminants. In addition, some well-known bunyaviruses like Rift Valley fever and Crimean-Congo haemorrhagic fever viruses continue to emerge in new geographical locations. In this short review we focus on newly identified viruses associated with severe haemorrhagic disease in humans in China and the US.

Figure 1

The phlebovirus genome. (a) Comparison of the coding strategy of the sandfly fever group (Rift Valley fever, RVFV) and Uukuniemi group (UUKV) genomes. RNAs are represented by thin lines (the length in nucleotides is given above each segment) and the mRNAs are shown as arrows (■ indicates host-derived sequences at 5′ end). Gene products, with their apparent M_r, are represented by coloured boxes. (b) Transcription and replication scheme of ambisense-sense phlebovirus S genome segment. The genome RNA encodes the N protein in the negative-sense and the NSs protein in positive-sense orientation, separated by an intergenic region that has the potential to form a hairpin structure. The proteins are translated from specific sub-genomic mRNAs, with the mRNA encoding NSs transcribed from the antigenome RNA.

Figure 2

Phylogeny of representative phleovirus proteins. The analogous protein from Gouleako virus, a mosquito-associated phlebovirus-like virus, was used as the outgroup in each case. Taken from Swei et al. [38^•].