Communicable Diseases

Yellow Fever


  • Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes. 
  • ​Yellow fever occurs when infected people introduce the virus into heavily populated areas with high mosquito density, and where most people have little or no immunity, due to lack of immunization.
  • A small proportion of patients who contract the virus develop symptoms. It can cause problems with the liver and kidneys and result in bleeding. 
  • The symptoms can be treated with rest, drinking fluids and taking painkillers and medications to alleviate the fever.
  • Yellow fever is prevented by an extremely effective vaccine, which is safe and affordable. A single dose of yellow fever vaccine is sufficient to grant sustained immunity and life-long protection against yellow fever disease.

Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes. The "yellow" in the name refers to the jaundice that affects some patients. The virus is endemic in Western, Eastern and Central Africa. It is also found in Central and South America, from Panama to Argentina. 

Yellow fever virus is transmitted by mosquitoes to humans. This mosquito species becomes active during the day, especially at sunrise. It also breeds inside or around houses and in ponds. When the female mosquito bites an infected person, it takes in the virus with the blood, which proceeds to breed inside the mosquito and penetrates its stomach. It finally stays in the salivary glands of the mosquito and the insect becomes a carrier of the disease throughout its whole life.

The yellow fever virus is transmitted by mosquitoes, belonging to the Aedes species (transmits the disease among humans) and Haemogogus species (transmits the disease among monkeys).

Incubation period:
3-6 days

Who is at risk?
Travelers who visit yellow fever endemic countries may bring the disease to countries free from yellow fever. Endemic areas include African countries and some tropical areas in South America.

Many people may not show symptoms. However, when they do arise, the most common ones are: 
  • Fever
  • Muscle pain
  • Headache
  • Loss of appetite
  • Nausea or vomiting
Most patients see an improvement in their health within 3-4 days.
A small percentage of patients enter a second, more toxic phase within 24 hours of recovering from initial symptoms. The symptoms include:
  • Return of the fever
  • Liver and kidneys being affected 
  • Dark urine
  • Stomachache with vomiting 
  • Bleeding in the mouth, nose, eyes or stomach 

When to see a doctor?
  • When symptoms of yellow fever appear while traveling in areas where the infection is prevalent
  • When symptoms appear upon the return from an endemic country

  • Jaundice
  • Pneumonia
  • Renal failure
  • Liver failure
  • Coma
  • Death

  • Medical history
  • Travel history
  • Laboratory tests

Currently, there is no specific type of medicine for yellow fever, but symptoms can be treated with rest, drinking fluids, taking painkillers, and medicines to reduce fever.  Aspirin or NSAIDs should be avoided, including: Naproxen, as they may increase the bleeding.

  • The yellow fever vaccine is safe, affordable and a single dose provides life-long protection against yellow fever disease. A booster dose of yellow fever vaccine might be needed in areas where the disease is continuously prevalent and if it has been over 10 years since it was last taken.
  • Avoid traveling to yellow fever endemic countries.
  • Avoid stagnant ponds and backfill them to get rid of mosquito breeding and spread.
  • Spray rooms with insecticide to kill the mosquitoes inside them in affected areas.
  • Wear garments that provide good body coverage to avoid mosquito bites, such as: Long-sleeve shirts, pants, and socks. These are best worn when you leave the house. 
  • Use insect repellents and mosquito nets.

Which groups are recommended to avoid taking the yellow fever vaccine? 
  • Children below the age of 9 months should not take the vaccine; however, it is advised that they take it if the risk of contracting the disease is higher than usual. 
  • Pregnant and breastfeeding women;
  • People above 60 years old;
  • People with weak immunity;
  • People who are allergic to any of the components of the vaccine.

Myths & Truths:
  • Myth:The virus can be transmitted by physical contact.
    • Truth: Yellow fever cannot be transmitted from a person to another through physical contact, such as touching or kissing. It can only be transmitted through the bites of a mosquito carrying the disease.

Clinical Education General Department
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Last Update : 16 August 2020 05:17 AM
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