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Image by Егор Камелев

The yellow fever virus is found in tropical and subtropical areas of Africa and South America and is spread to people by the bite of an infected mosquito. 

The most effective way to prevent infection from the Yellow Fever virus is to prevent mosquito bites. Mosquitoes bite during the day and night. Use insect repellent, wear long-sleeved shirts and pants, treat clothing and gear, and get vaccinated before traveling if vaccination is recommended.

A safe and effective yellow fever vaccine has been available for more than 80 years.


  • A single dose provides lifelong protection for most people.

  • The vaccine is a live, weakened form of the virus given as a single shot.

  • The vaccine is recommended for people aged nine months or older and traveling to or living in areas at risk for yellow fever virus in Africa and South America.

  • Yellow fever vaccine may be required for entry into certain countries.

There are three phases:


Incubation Phase


Three to six days after contracting yellow fever, typically there are no signs or symptoms.


Acute phase


Once the infection enters the acute phase, the following symptoms may appear:


  • Fever

  • Headache

  • Muscle aches, particularly in your back and knees

  • Sensitivity to light

  • Nausea, vomiting or both

  • Loss of appetite

  • Dizziness

  • Red eyes, face, or tongue


These signs and symptoms usually improve and are gone within several days.


Toxic phase


Although signs and symptoms may disappear for a day or two following the acute phase, some people with acute yellow fever enter a toxic phase. Acute signs and symptoms return during this phase, and more severe and life-threatening ones also appear. 


These can include:


  • Yellowing of the skin and the whites of eyes (jaundice)

  • Abdominal pain and vomiting, sometimes of blood

  • Decreased urination

  • Bleeding from your nose, mouth, and eyes

  • Slow heart rate

  • Liver and kidney failure

  • Brain dysfunction, including delirium, seizures, and coma


The toxic phase of yellow fever can be fatal.

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