Yellow fever begins after an incubation period of three to six days. Most cases only cause a mild infection with fever, headache, chills, back pain, loss of appetite, nausea, and vomiting. In these cases the infection lasts only three to four days. In fifteen percent of cases, however, sufferers enter a second, toxic phase of the disease with recurring fever, this time accompanied by jaundice due to liver damage, as well as abdominal pain. Bleeding in the mouth, the eyes and in the gastrointestinal tract will cause vomitus containing blood (giving the name black vomit). The toxic phase is fatal in approximately 20% of cases, making the overall fatality rate for the disease 3% (15% * 20%).
Yellow fever is caused by the yellow fever virus, a 40 to 50 nm wide enveloped RNA virus belonging to the family Flaviviridae. The positive sense single-stranded RNA is approximately 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 non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, NS5); the enumeration corresponds to the arrangement of the protein coding genes in the genome. The viruses infect amongst others monocytes, macrophages and dendritic cells. They attach to the cell surface via specific receptors and are taken up by an endosomal vesicle. Inside the endosome, the decreased pH induces the fusion of the endosomal membrane with the virus envelope. Thus, the capsid reaches the cytosol, decays and releases the genome. Receptor binding as well as membrane fusion are catalyzed by the protein E, which changes its conformation at low pH, which causes a rearrangement of the 90 homodimers to 60 homotrimers.
Yellow fever is caused by the yellow fever virus, a 40 to 50 nm wide enveloped RNA virus belonging to the family Flaviviridae. The positive sense single-stranded RNA is approximately 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 non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, NS5); the enumeration corresponds to the arrangement of the protein coding genes in the genome. The viruses infect amongst others monocytes, macrophages and dendritic cells. They attach to the cell surface via specific receptors and are taken up by an endosomal vesicle. Inside the endosome, the decreased pH induces the fusion of the endosomal membrane with the virus envelope. Thus, the capsid reaches the cytosol, decays and releases the genome. Receptor binding as well as membrane fusion are catalyzed by the protein E, which changes its conformation at low pH, which causes a rearrangement of the 90 homodimers to 60 homotrimers.
