Yellow fever is a viral disease which is transmitted to humans by mosquitoes. 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.
The symptoms of the first stage of the disease appear 3 - 6 days after exposure, and include fever, nausea, vomiting, flushed face, constipation, stomach
discomfort, headache, muscle pains (especially in the neck, back and legs), restlessness, and irritability. A remission period follows these symptoms, and mild cases of yellow fever end here.
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.