Yellow fever is an illness which is caused by a virus. The illness can cause bleeding problems. It is called yellow because the skin sometimes becomes yellow, like it does with jaundice. There is a vaccine which can stop the disease, but many people in Africa and South America are not vaccinated against it. The World Health Organization say that 200,000 people are made ill with yellow fever every year, and that 30,000 people die from it. The diseases that spread from mosquito, or as widely disputed, rats, and also from an infected person through air, water, and food to a healthy person is called communicable disease. Yellow fever is a communicable disease, and it is highly contagious. It peaked in 1842, killing hundreds of people.
Yellow fever is spread through the bite of an infected mosquito.