Prevention of yellow fever

Yellow fever is a viral illness caused by the bite of a mosquito carrying the yellow fever virus. The infection is only passed from mosquito to human; there is no human-to-human transmission. The name of the disease originated from the yellow discoloration of the skin of some patients (known as jaundice). Yellow fever can cause only mild illness – with only fever and headache – or it can cause a much more serious illness, with damage to every major organ system (heart, kidneys, liver) and eventually massive bleeding (hemorrhage) due to liver failure.

Who's At Risk?

• Travellers to (and inhabitants of) endemic areas.

• Travellers to (and inhabitants of) tropical rain forests.

• Anyone in these areas who is unvaccinated.

• Anyone in these areas working outdoors at dawn or dusk, or those who sleep without a mosquito net.

• There is a risk that a traveller to an endemic area could return with yellow fever, and while person-to-person contact is not contagious, an infected traveller could reintroduce yellow fever back into the local mosquito population.

Signs and Symptoms

During the first three to six days (the incubation period) after you've contracted yellow fever, you won't experience any symptoms. After this, the infection enters an acute phase and then, in some cases, a toxic phase that can be life-threatening. Symptoms include:

  • Fever
  • Chills
  • Vomiting
  • Headache
  • Muscle aches
  • Lower-back pain
  • Sensitivity to light
  • Dizziness
  • Loss of appetite
  • Red eyes, face or tongue
  • Abdominal pain
  • Bleeding from the nose, eyes and mouth
  • Brain dysfunction, including delirium, seizures and coma
  • Yellow color to the white of the eye (jaundice), caused by liver failure
  • Lack of urine output, caused by kidney failure • Internal bleeding caused by liver failure (hemorrhage)
  • Slow heart rate
  • Death


International law requires travellers crossing the borders of countries where yellow fever is endemic to have yellow fever vaccinations. A safe and highly effective vaccine prevents yellow fever. Yellow fever is found in sub-Saharan Africa and parts of South America. If you plan to travel in these areas, talk with your doctor at least 10 days, but preferably three to four weeks, before the start of your trip. After you have been vaccinated you will be issued with a Yellow Fever Certificate. The certificate only becomes valid ten days after vaccination, and stays valid for ten years. Side effects are usually mild, lasting five to 10 days, and may include headaches, low-grade fevers, muscle pain, fatigue and soreness where the injection was administered.

More-significant reactions — such as developing a syndrome similar to actual yellow fever, inflammation of the brain (encephalitis) or death — can occur, most often in infants and older adults. The vaccine is considered safest for those between the ages of 9 months and 60 years. Talk to your doctor about whether the yellow fever vaccine is appropriate if your child is younger than 9 months, if you have a weakened immune system (immune compromised), or if you're older than 60 years.

Mosquito protection

In addition to getting the vaccine, you can help protect yourself against yellow fever by protecting yourself against mosquitoes. To reduce your exposure to mosquitoes:

• Avoid unnecessary outdoor activity when mosquitoes are most active (evening).

• Wear long-sleeved shirts and long pants when you go into mosquito-infested areas.

• Stay in air-conditioned or well-screened housing.

• If your accommodationis not equipped with good window screens or air-conditioning, use mosquito nets. Nets that have been pre-treated with insecticide offer additional protection.

To ward off mosquitoes with repellent, use both non-skin repellent such aspermethrin on clothing, shoes, camping gear and mosquito netsand skin repellent (products with the active ingredients DEET, IR3535 or picaridin). Keep in mind that chemical repellents can be toxic, and use only the amount needed for the time you'll be outdoors. Don't use DEET on the hands of young children or on infants under 2 months of age. Instead, cover your infant's stroller or playpen with mosquito netting when outside.

According to the Centres for Disease Control and Prevention, oil of lemon eucalyptus, a more natural product, offers the same protection as DEET when used in similar concentrations. But these products should not be used on children younger than age 3.

Treatments and drugs

No antiviral medications have proved helpful in treating yellow fever. As a result, treatment consists primarily of supportive care in a hospital. This includes providing fluids and oxygen, maintaining adequate blood pressure, replacing blood loss, providing dialysis for kidney failure, and treating any other infections that may develop. Some people receive transfusions of plasma to replace blood proteins that improve clotting.

If you have yellow fever, your doctor will most likely recommend that you stay indoors, away from mosquitoes, to avoid transmitting the disease to others. Once you have had yellow fever, you'll be immune to the disease for the rest of your life.


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