Yellow Fever



An infected mosquito passes the virus through a bite on the skin.

Mosquito Bite
Mosquito bite
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Risk Factors

Things that may raise the risk of yellow fever are:

  • Living in or going to places where yellow fever is common
  • Not getting a yellow fever vaccine
  • Not using mosquito protection



Symptoms appear within a week after a mosquito bite. The acute phase lasts 3 to 4 days, then symptoms go away. At the end of the acute phase, some people move to the toxic phase.

Some people may not have symptoms. Those who do may have:

Acute phase:

  • Fever and chills
  • Headache
  • Muscle pain
  • Lack of hunger
  • Nausea or vomiting

Toxic phase:

  • High fever
  • Belly pain
  • Bleeding from the gums, nose, eyes, or stomach
  • Vomit that appears black due to bleeding
  • Yellowing of the skin and eyes known as jaundice
  • Confusion, seizure, or coma


The doctor will ask about symptoms and past health. Questions may also be asked about any recent travel. A physical exam will be done. Yellow fever can be confirmed by blood tests.



The goal of treatment is to ease symptoms. It may include:

  • Fluids by mouth or IV to prevent dehydration
  • Medicines to lower fever and ease pain
  • Dialysis to help kidneys filter waste
  • A transfusion to replace blood lost through bleeding
Dialysis pump
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Yellow fever can be prevented with a vaccine.

The risk of yellow fever may also be lowered by avoiding mosquito bites. Things that may help are:

  • Covering up the skin
  • Using insect repellent, netting, and screens
  • Staying inside between dusk and dark

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.