Updated April 2011

What Is Yellow Fever?

Yellow fever is a disease caused by a virus (flavirirus) transmitted by the bite of an infected mosquito. The disease gets its name from the yellowing of the skin and eyes (jaundice) that occurs when the virus attacks the liver. Yellow fever can be prevented by a vaccine.

How Do People Get Yellow Fever?

Yellow fever is spread through the bite of infected mosquitoes. Several different species of Aedes Haemagogus mosquitoes transmit the virus. The mosquitoes either breed around houses (domestic), in the jungle (wild), or in both habitats. Yellow fever epidemics occur in urban areas when infected people carry the disease from rural or jungle areas into densely populated areas.

Where Is Yellow Fever a Concern?

Worldwide, 90% of yellow fever cases occur in Africa and 10% in the Americas. Yellow fever is endemic (always present) in Africa, typically in countries situated at or around the equator; and in many tropical areas of South America, including Bolivia, Brazil, Colombia, Ecuador and Peru. Several Caribbean islands are also at low risk for epidemics. Yellow fever is not endemic in Asia, but there is potential for epidemics. For North American residents, the disease is only a risk when traveling to tropical countries.

What Are the Symptoms of Yellow Fever?

Symptoms of yellow fever include sudden onset of fever, headache, joint pain, loss of appetite, abdominal pain, vomiting and dehydration. Most people infected with yellow fever recover after this stage. Symptoms can appear three to six days after becoming infected.

In about 15% of patients, yellow fever can lead to severe illness, including shock, internal bleeding, jaundice and organ failure. Those who recover from the severe stage of illness recover without significant organ damage. Death occurs in about 15-50% of cases of severe yellow fever illness.

How Is Yellow Fever Treated?

There is no specific treatment for yellow fever. People infected with yellow fever can receive care to treat dehydration and fever.

How Can Yellow Fever Be Prevented?

A single dose of yellow fever vaccine provides protection (immunity) against the virus for 10 years or more. If a person is at continued risk of yellow fever infection, a booster dose is needed every 10 years. Adults and children over nine months of age can take this vaccine.

How Can I Protect Myself from Yellow Fever When Traveling?

Consult a doctor, nurse or health care provider, or visit a travel health clinic at least six weeks before you travel. For entry into certain countries, proof of immunization against yellow fever is required by law.

Practice protective measures to avoid mosquito bites including:

  • Use insect repellent on exposed skin. Of the insect repellents registered in Canada, those containing DEET are the most effective.
  • Wear proper clothing to cover up, including light-coloured, long-sleeved, tucked-in shirts, long pants, closed shoes (not sandals), and a hat.
  • Be aware that mosquitoes that spread yellow fever usually bite during the day, particularly two to three hours after dawn and during the early evening. Take extra care during these times to avoid mosquito bites.
  • Sleep under a bed net, preferably one treated with an insecticide.
  • Where possible, stay in a well-screened or completely enclosed air-conditioned place.
  • Apply a permethrin insecticide to tents and clothing and other travel gear for greater protection.

Where Can I Find More Information?

For more information on the prevention of yellow fever please visit the Public Health Agency of Canada – Yellow Fever website

Adapted From

Public Health Agency of Canada – Yellow Fever Travel Health fact sheet
World Health Organization – Yellow Fever fact sheet
Centre for Disease Control – Yellow Fever Prevention