Ok so I not up to speed, but...

Yellow fever (also called yellow jack, black vomit or vomito negro, or sometimes American Plague) is an acute viral disease.[1] It is an important cause of hemorrhagic illness in many African and South American countries despite existence of an effective vaccine. The yellow refers to the jaundice symptoms that affect some patients.[2]

Yellow fever has been a source of several devastating epidemics. During the 1802 Haitian Revolution, French soldiers were attacked by yellow fever: More than half of the army perished due to the disease.[3] 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.

Despite the costly and sacrificial breakthrough research by Cuban physician Carlos Finlay, American physician Walter Reed, and many others over 100 years ago, unvaccinated populations in many developing nations in Africa and Central and South America continue to be at risk.[4] As of 2001, the World Health Organization (WHO) estimates that yellow fever causes 200,000 illnesses and 30,000 deaths every year in unvaccinated populations.[5]