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Information On Yellow Fever

Mosquito on a human arm

What is yellow fever?

Yellow fever is a viral infection spread by certain types of mosquito. It is most common in sub-Saharan Africa and South America. There is currently no cure for yellow fever and as it can be fatal - around 8 in 100 people die once infected - it is advised that most people travelling to a high risk area gets vaccinated against the virus beforehand.

How is yellow fever spread?

Yellow fever is a flavivirus commonly transmitted by the bite of the Aedes aegypti mosquito in urban and rural areas. In forested areas, yellow fever can also be transmitted by other types of mosquito. Mosquitoes become carriers by biting monkeys or humans who are infected with the virus, enabling them to pass the infection on to any other monkeys or humans they later bite. You are less likely to be bitten by a mosquito and catch yellow fever if you wear protective clothing and mosquito repellent.

It is important to note that yellow fever is not contagious between humans and cannot be passed on through person-to-person contact.

High risk areas for yellow fever

  • Sub-Saharan African countries (including Angola, Cameroon, Ethiopia, Kenya, Nigeria, Senegal and Uganda)
  • South American countries (including Brazil, Ecuador and Venezuela)
  • Trinidad

For a full, up-to-date list of yellow fever risk areas, visit NHS Fit For Travel.

Please note that to visit any of the following countries you must be vaccinated against yellow fever:

  • Angola
  • Benin
  • Burkina Faso
  • Burundi
  • Cameroon
  • Central African Republic
  • Republic of Congo
  • Democratic Republic of Congo
  • Côte d'Ivoire
  • French Guiana
  • Gabon
  • Guinea-Bissau
  • Liberia
  • Mali
  • Niger
  • Rwanda
  • Sierra Leone
  • Togo

What are the symptoms of yellow fever?

Yellow fever has an incubation period of 3 to 6 days, meaning that once you have been infected it could take up to a week for symptoms to appear.

The initial symptoms of yellow fever are not hugely distinctive, and resemble the symptoms of other viral infections such as malaria and typhoid fever. Early indications include:

  • fever
  • headache
  • chills
  • nausea and vomiting
  • muscle pain
  • loss of appetite

Most people will recover from the virus after three or four days of these symptoms. However some people (around 15%) will worsen and enter what is referred to as the ‘toxic phase’. Symptoms include:

  • abdominal pain
  • jaundice
  • kidney failure
  • bleeding from the mouth, eyes, nose and stomach

Around 50% of people who progress to this phase will die from the virus - those who survive will typically be immune from yellow fever for the rest of their lives.

How is yellow fever treated?

Treatment for yellow fever must start with diagnosis. As it can be difficult to diagnose yellow fever solely by its symptoms (which resemble those of other infectious diseases such as malaria), diagnosis must usually be confirmed with a blood test.

There is no cure for yellow fever, so subsequent treatment involves painkillers such as ibuprofen and paracetamol (to soothe the fever and ease muscle pain) and drinking plenty of water (to combat dehydration).

Severe symptoms must be treated in a hospital and may require a blood transfusion or kidney dialysis.

The yellow fever vaccination

The best way to avoid being infected with yellow fever is to get vaccinated against it before you travel to a high risk area. In the UK, Stamaril is currently the only licensed yellow fever vaccine.

Stamaril is injected in a single dose into the muscle, by a trained doctor or nurse. Some people may require a booster vaccine later in life, however the majority of people will not.

Most people will be suitable for the vaccination, but it will not be safe for some people to receive. Unsuitable candidates can include people who:

  • are HIV-positive, or have a weakened immune system
  • are pregnant or breastfeeding
  • are over 60 years old (the risk of having a bad reaction to Stamaril increases as you get older)

If you fall into one of the above categories, you can speak to your doctor and have your suitability for the vaccine assessed. In the case of HIV-positive people, blood tests may be taken to determine whether Stamaril can be safely administered.

Side effects

Some side effects of the yellow fever vaccination can include:

  • swelling, bruising or pain around the injection site
  • nausea or vomiting
  • diarrhoea
  • muscle pain
  • fever

In some cases, people can have an allergic reaction to the vaccine. If you have allergic symptoms such as a rash on the skin, difficulty breathing or loss of consciousness you should seek medical help immediately. In some cases an allergic reaction to the yellow fever vaccine can be fatal.

Are there other ways to avoid catching yellow fever?

In addition to getting vaccinated, you can help reduce your chances of getting bitten by a mosquito in the first place by:

  • wearing long-sleeved clothing
  • wearing mosquito repellent (DEET is the most effective)
  • using mosquito nets

If you would like to get vaccinated, you can talk to your doctor of visit MASTA (Medical Advisory Service for Travellers Abroad).