ReviewYellow fever virus: Genetic and phenotypic diversity and implications for detection, prevention and therapy

•Yellow fever virus (YFV) is a threat to human health in Africa and South America.•Multiple genotypes of YFV have been described but only a single serotype.•Diversity of YFV is unlikely to hinder development of new therapies/vaccines.•Relationships between genotype and virulence/transmission are not well understood.•More extensive phenotypic comparisons of YFV strains/genotypes are needed.

Yellow fever virus (YFV) is the prototypical hemorrhagic fever virus, yet our understanding of its phenotypic diversity and any molecular basis for observed differences in disease severity and epidemiology is lacking, when compared to other arthropod-borne and haemorrhagic fever viruses. This is, in part, due to the availability of safe and effective vaccines resulting in basic YFV research taking a back seat to those viruses for which no effective vaccine occurs. However, regular outbreaks occur in endemic areas, and the spread of the virus to new, previously unaffected, areas is possible. Analysis of isolates from endemic areas reveals a strong geographic association for major genotypes, and recent epidemics have demonstrated the emergence of novel sequence variants. This review aims to outline the current understanding of YFV genetic and phenotypic diversity and its sources, as well as the available animal models for characterizing these differences in vivo. The consequences of genetic diversity for detection and diagnosis of yellow fever and development of new vaccines and therapeutics are discussed.