Yellow fever is caused by a virus and at one time was common in Africa and South America. Human beings get the disease from the bite of infected mosquitoes. In severe cases the liver is involved, and the skin becomes yellow because of jaundice.
Along with jaundice and high fever, symptoms include headache, backache, and internal bleeding or hemorrhage. In early stages of the disease, the edges and tip of the tongue are bright red, but later become brownish. In severe cases the death rate is high.
Fever is the only common symptom in a mild case, and fortunately most cases are mild. After recovery people are immune for the rest of their lives.
Before it was known that yellow fever is transmitted by mosquitoes, hundreds of people died from it each year. Today, mosquito control and the development of a vaccine has almost eliminated the disease.
