Yellow fever was the first illness shown to be transmissible by filtered human serum and transmitted by mosquitoes, by Walter Reed around 1900. The positive-sense, single-stranded RNA is around 11,000 nucleotides long and has a single open reading frame encoding a polyprotein. Host proteases cut this polyprotein into three structural (C, prM, E) and seven nonstructural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, NS5); the enumeration corresponds to the arrangement of the protein coding genes in the genome. Minimal yellow fever virus (YFV) 3'UTR region is required for stalling of the host 5'-3' exonuclease XRN1. The UTR contains PKS3 pseudoknot structure which
Yellow fever vaccine fever certificate of vaccination for travelers. Increases in cases of yellow fever in endemic areas of Africa and South America in the 1980s were addressed by the WHO Yellow Fever Initiative launched in the mid-2000s. The initiative was supported by the Gavi Alliance, a collaboration of the WHO, UNICEF, vaccine manufacturers, and private philanthropists such as the Bill & Melinda Gates Foundation. Gavi-supported vaccination campaigns since 2011 have covered 88 million people in 14 countries considered at "high-risk" of a yellow fever outbreak (Angola was considered "medium risk"). Activities of the Yellow Fever Initiative are managed through an international coordinating