Yellow fever

What is Yellow fever
Yellow fever is a hemorrhagic fever caused by a virus spread by a particular species of mosquito. It is most common in areas of Africa and South America, affecting travelers to and residents of those areas.
In mild cases, yellow fever causes fever, headache, nausea and vomiting. But yellow fever can become more serious, causing bleeding (hemorrhaging), heart, liver and kidney problems. Up to 50 percent of those with the more severe form of yellow fever die of the disease.
There is no specific treatment for yellow fever. But getting a yellow fever vaccine before traveling to an area in which the virus is known to exist can protect you from the disease.

Symptoms
During the first three to six days after you've contracted yellow fever — the incubation period — you won't experience any signs or symptoms. After this, the virus enters an acute phase and then, in some cases, a toxic phase that can be life-threatening.
Acute phase Once the yellow fever virus enters the acute phase, you may experience signs and symptoms including:
Fever
Headache
Muscle aches, particularly in your back and knees
Nausea, vomiting or both
Loss of appetite
Dizziness
Red eyes, face or tongue
These signs and symptoms usually improve and are gone within three to four days.

Toxic phase

Although signs and symptoms may disappear for a day or two following the acute phase, 15 percent of those with acute yellow fever then enter a toxic phase. During the toxic phase, acute signs and symptoms return and more severe and life-threatening ones also appear. These can include:
Yellowing of your skin and the whites of your eyes (jaundice)
Abdominal pain and vomiting, sometimes blood
Decreased urination
Bleeding from the nose, mouth and eyes
Heart dysfunction (arrhythmias)
Liver and kidney failure
Brain dysfunction including delirium, seizures and coma
About 20 percent to 50 percent of those who enter the toxic phase die of the disease. The rest usually recover without significant problems.