Yellow Fever

Yellow fever is a mosquito-borne virus that is common in parts of South America and Africa. There are an estimated 200,000 cases of yellow fever every year, resulting in 30,000 deaths, 90% of which occur in Africa. Many countries require proof of yellow fever vaccination for entry into the country as a means of reducing transmission of the disease.


The acute phase of yellow fever is characterized by the following symptoms:

  • Fever
  • Chills
  • Headache
  • Body aches and muscle aches
  • Loss of appetite
  • Nausea and vomiting

Symptoms typically take 3-6 days to develop following exposure to the virus from an infected mosquito. Many patients have only acute yellow fever, which will resolve in three to four days. About 15% of patients enter a second phase of illness following the acute phase. In this second, more toxic phase, patients will have:

  • Recurring high fever
  • Jaundice
  • Abdominal pain and vomiting
  • Bleeding from the mouth, nose, eyes or stomach
  • Blood in vomit and feces
  • Reduced kidney function

Half of all toxic phase patients will die within 10 to 14 days of entering the toxic phase.


The CDC recommends that travelers going to countries in which yellow fever is endemic get a yellow fever vaccine at least 10 days before their trip. Some countries will require a stamped International Certificate of Vaccination or Prophylaxis in order to enter the country. A single dose of yellow fever vaccine is sufficient to provide life-long protection against yellow fever disease in 99% of people vaccinated.

In addition to getting the vaccine, you can take other precautions to prevent mosquito bites:

  • Wear clothing that covers exposed skin, including long shirts and pants
  • Use repellants with a high percentage of active ingredient
  • Use permethrin-treated clothing and gear
  • Stay and sleep in rooms with screens or air conditioning
  • Use a bed net if sleeping in an area that is exposed to the outdoors

Visit the CDC’s Travelers Health website to learn more about the diseases you need to protect yourself against based on the type of traveler you are and your travel destination.