This micrograph shows multiple virions of the Yellow Fever Virus at a magnification of X234,000. Yellow fever, a viral disease that ranges in severity from an influenza-like syndrome to severe hepatitis or hemorrhagic fever, is found primarily in sub-Saharan Africa and tropical South America. In Africa, where most cases are reported, a variety of vectors are responsible for transmitting the virus. The case fatality rate is greater than 20%, and infants and children are at greatest risk for infection.