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What is Yellow Fever?

What is yellow fever?

Yellow fever is an acute (short duration) viral infection, which is spread by infected mosquitoes. Yellow fever is called that because it can cause infected people to develop jaundice, which is yellowing of the skin and eyes. Yellow fever is a dangerous infection that can cause multiple organ failure, hemorrhagic fever (which causes bleeding from the mouth, eyes, ears, and stomach), and even death. However, yellow fever is easily prevented by the yellow fever vaccine.

How is yellow fever spread?

Yellow fever is spread through the bite of an infected female mosquito. Mosquitoes get the virus by biting an infected human or other primate and drinking their blood, and can also pass it to their offspring if they are infected when they lay eggs. The yellow fever virus lives in the saliva of an infected mosquito, which it injects into the bloodstream when it bites a human.

There are three transmission cycles for yellow fever: jungle, intermediate, and urban.

Jungle cycle – in rainforests and jungles, monkeys act as a reservoir for the yellow fever virus. Monkeys that have been infected with yellow fever are bitten by wild mosquitoes, which then bite and infect other monkeys. Humans visiting these rainforests and jungles can then be bitten by an infected mosquito and spread the virus to urban areas.

Intermediate cycle – also known as the savannah cycle, this cycle occurs only in regions of Africa where humans work or live close to rainforests or jungles. In this cycle, mosquitoes transmit the yellow fever virus between humans and monkeys.

Urban cycle – humans can bring the yellow fever virus into towns and cities if they were infected in the jungle. Mosquitoes that live and breed in urban areas can bite infected humans and then transmit the virus to other humans.

Most cases of yellow fever are transmitted by the mosquito aedes aegypti, which is mostly found in regions of Africa and South America, but this mosquito can also be found in other tropical and subtropical regions across the world.

Infected humans cannot transmit yellow fever to other humans just by being in close contact but it can spread if you come into direct contact with infected human blood, such as sharing contaminated needles.

Where is yellow fever found?

Yellow fever is usually found in tropical and subtropical areas of sub-saharan Africa and South America. Yellow fever can also be found in some areas of Central America and the Caribbean. Some countries may also require that you have a yellow fever certificate to prove that you have been vaccinated against yellow fever before you can enter the country.

You can enter your holiday destination into our travel vaccination checker to find out if the yellow fever vaccine is recommended for your travels, or if certification is required for entry.

You can also find a full list of the at-risk countries for yellow fever here.

Is yellow fever serious?

Yellow fever can be an incredibly serious disease. But, most people who are infected will develop the early symptoms of yellow fever, and will make a full recovery after 3 to 4 days.

However, if your symptoms progress to a stage called “the toxic phase” and you develop jaundice, there is a 20% to 50% chance that it will be fatal. Because of this, it is highly recommended that you get vaccinated against yellow fever if you are travelling to a country where there is a risk of infection.

What are the signs and symptoms of yellow fever?

Early signs of yellow fever include:

  • fever
  • nausea
  • vomiting
  • tiredness
  • sensitivity to light

The symptoms can progress to:

  • abdominal pain
  • kidney failure
  • seizures
  • coma
  • internal bleeding
  • bleeding from mouth, nose, and eyes
  • yellowing of the eyes and skin (jaundice)

You can get more specific information on our page about the symptoms of yellow fever.

How is yellow fever treated?

There is currently no specific cure for yellow fever, so if you are infected then your treatment will be designed to help manage the symptoms while your immune system fights off the virus.

Painkillers – some of the early symptoms of yellow fever, such as headache, muscle aches and fever, can be treated with medications like paracetamol or ibuprofen.

Drink plenty of fluids – yellow fever can lead to dehydration through loss of fluids, especially if you are feverish or vomiting. Dehydration can limit your body’s ability to effectively fight off the yellow fever virus, which could lead to developing more advanced symptoms, so it is important to drink plenty of water.

Hospital treatment – in severe cases of yellow fever, where more advanced symptoms start to appear, then immediate hospital treatment is required. If you think you have symptoms of yellow fever and do not recover within 3 to 6 days, or start to develop any of the advanced symptoms, seek medical attention immediately so you can be diagnosed and treated.

How do you prevent yellow fever?

Yellow fever vaccine – yellow fever is easily preventable with a single dose of the yellow fever vaccine. The yellow fever vaccine is a live vaccine, which means it contains a small amount of the live yellow fever virus. Your immune system is exposed to this virus so it can develop antibodies that can fight off the yellow fever virus in the future, without risking a full-blown infection. The yellow fever vaccine provides immunity against yellow fever for life, so you’ll only ever need one jab. You can get the yellow fever vaccine at certain Superdrug Health Clinics that have been registered as Yellow Fever Centres.

Avoid mosquito bites – mosquitoes that spread yellow fever mostly like to feed at dusk and at dawn, so if you are out at that time it’s best to wear clothes that cover your arms and legs, and spray on plenty of insect repellent to keep them at bay. You should also put mosquito netting over your bed to make sure you can’t get bitten while you sleep.

It is important to take precautions to avoid insect bites even if you have been vaccinated against yellow fever as they can spread other diseases such as dengue fever, malaria, and zika. You can find more specific information on our page on how to avoid insect bites.