Yellow fever is a serious viral illness with no cure. It is contracted through the bite of female mosquitoes found in areas in the South American rainforest, and in areas throughout Africa. The mosquitoes are vectors for yellow fever, and pass it by biting an affected monkey or person, and then biting and infecting someone else.

In South America, the disease is usually only contracted in dense rain forests where monkeys are present. It is sometimes called jungle yellow fever. One is most at risk for getting a bite from an infected mosquito during the day, and all going into jungle areas of South America are warned to wear insect repellent and spray sleeping quarters.

Yellow fever contracted in Africa is usually passed from person to person via mosquito bite and is called urban yellow fever. Occasional outbreaks occur in various parts of Africa, and one is just as likely to become infected in a city or town, as in jungle areas. Similar precautions should be taken to avoid infection. In particular, people should be wary of bites during the day, use insect repellent with DEET, and spray beds, bed nets, and clothing with insecticide to avoid bites.

Yellow fever once caused great problems in other areas of the world. Yellow fever epidemics during the Spanish American War, and particularly the epidemic in Philadelphia in the 19th century killed thousands of people. Early in the 20th century, scientists discovered the cause of yellow fever, and soon afterward, a vaccine was developed which has essentially eradicated yellow fever in the US, and other parts of the world. Vaccines are less available to people in poorer areas. Thus parts of Africa and South America are prime targets for contracting the disease because people do not have the vaccine available.

Anyone traveling to an area where yellow fever is a problem receives a vaccination that can protect one from contagion for up to ten years. People traveling from areas with yellow fever, may also need to be cleared of being contagious with the disease, and may require a vaccination before admission to various countries that are yellow fever free.