Definition
Yellow fever is a viral infection transmitted by mosquitoes and characterized by fever, jaundice, kidney failure, and bleeding.

Causes, incidence, and risk factors

Yellow fever is caused by an arbovirus, a small virus transmitted by the bite of mosquitoes. This disease is common in South America and in sub-Saharan Africa. Humans and monkeys are both hosts in the transmission cycle of this infection.

While yellow fever can affect individuals of all ages, the elderly have a higher risk of severe infection. If a person is bitten by an infected mosquito, symptoms usually develop three to six days later.

Yellow fever can be divided into three stages:

Early stage: headache, muscle aches, fever, loss of appetite, vomiting, and jaundice are common.
Period of remission: fever and other symptoms resolve -- most individuals will recover at this stage, yet up to 15% may move onto the third, most dangerous stage.
Period of intoxication: characterized by multi-organ dysfunction -- liver and kidney failure, bleeding disorders/hemorrhage, brain dysfunction including delirium, seizures, coma, shock, and in up to 30% individuals, death.

Prevention

If you will be traveling to an area where yellow fever is common, use mosquito repellents, wear clothing that fully covers your body, and sleep in screened housing. Notify your health care provider at least 10-14 days prior to travel to determine whether you should be vaccinated against yellow fever.

Symptoms

Fever
Headache
Muscle aches (myalgia)
Vomiting
Red eyes, face, tongue
Jaundice
Bleeding (may progress to frank hemorrhage)
Decreased urination
Arrhythmias, heart dysfunction
Vomiting blood
Delirium
Seizures
Coma

Signs and tests

A person with advanced yellow fever may show signs of liver failure, renal failure, and shock.

If you have symptoms of yellow fever, tell your health care provider if you have traveled to areas where the disease is known to thrive. The diagnosis is confirmed by blood tests that reveal the virus, viral antigens, or antibodies.