Yellow fever is an acute disease of certain tropical regions, characterized by fever and jaundice. The disease is shared with other primates. Transmission from host to host is accomplished via species of Aedes mosquitoes in Africa and Haemagogus and Aedes in South America.
Mild cases of yellow fever include symptoms of fever, nausea, vomiting, flushed face, constipation, stomach discomfort, headache, muscle pains, restlessness, and irritability. In severe cases, the fever falls somewhere 2 - 5 days after onset, and a remission of several hours or days follows. The fever recurs, but the pulse remains slow, and the patient develops the classic symptoms of yellow fever, including jaundice (yellowed skin and eyes) and black, coffee-ground vomit.
This disease occurs in many countries in Africa and South America, and it is believed that the incidence of yellow fever is greatly underreported among local populations. For travellers to rural parts of yellow-fever risk areas, the risk of contracting infection is high, even if the country has not officially reported the disease and does not require evidence of immunization on entry. There is a more than 60% percent chance of contracting infection in unimmunized adults in these circumstances.