Yellow fever (also called yellow jack, black vomit or vomito negro in Spanish, or sometimes American Plague) is an acute viral disease. It is an important cause of hemorrhagic illness in many African and South American countries despite existence of an effective vaccine. The yellow in the disease name refers to the jaundice that affects some patients.
Yellow fever has been a source of several devastating epidemics. During one of Napoleon's campaigns to Haiti in 1802, the troops were attacked by yellow fever. More than half of the army perished due to the disease. Outbreaks followed by thousands of fatalities occurred periodically in other Western Hemisphere locations until research which included human volunteers (some of whom died) led to an understanding of the method of transmission to humans (primarily by mosquitos) and development of a vaccine and other preventative efforts in the early 20th century. (More...)