Yellow fever is a very serious viral disease which can be fatal.

It is transmitted by a type of mosquito that lives in tropical regions of Africa and South America, but not Asia.

You can protect yourself by having a vaccination before you travel to certain countries.

What causes yellow fever and who can get it?

Anyone who has not had a vaccination against yellow fever and is bitten by a mosquito carrying the disease can get sick.

The virus is introduced into the bloodstream via the saliva of the mosquito as it bites.

It is then transported around the body and reproduces itself inside human cells, initially lymph glands and then the liver.

During replication the cells are damaged. In serious cases massive cell destruction occurs leading to failure of many of the body’s organs, bleeding and death.

How dangerous is yellow fever?

Yellow fever can be fatal. About five per cent of local people who get yellow fever die from the condition, but death rates can be much higher in travellers (up to 50 per cent).

What are the signs and symptoms of yellow fever?

In mild cases of yellow fever, the symptoms are similar to flu.

In serious cases a person can develop a high temperature and may have a series of after-effects, such as internal bleeding and kidney failure.

The classic feature of yellow fever is hepatitis, which is also the reason for the yellow colouring of the skin called jaundice that gives the fever its name.

How is yellow fever normally diagnosed and treated?

It is sometimes difficult to diagnose yellow fever because in the early stages it can look like lots of other conditions. Initial symptoms include:

• Muscle aches
• Fever
• Headache
• Nausea
• Vomiting

If your doctor suspects you are infected they will take a blood sample to be tested.

There are no medicines that are effective against this virus and in serious cases a patient will have to be hospitalised, monitored and have their symptoms treated. This can include giving fluids through a drip.

In mild cases, the pain may be relieved with simple painkillers (but avoid aspirin).

Can yellow fever be prevented?

There's a vaccine that's very effective against yellow fever. You need to have the vaccine at least 10 days before you travel. Current advice is to have it repeated every 10 years.

Apart from vaccination, prevention of mosquito bites is the best way of avoiding yellow fever.

But because the disease is so dangerous, taking a chance and going without vaccination is absolutely not recommended.

When to ask for medical help

You should ask for medical help if you suspect you may have yellow fever.

The illness may be mild with fever, headache, back pain, poor appetite, nausea and vomiting.

But it may be very serious and result in bleeding as well as liver inflammation (hepatitis). The bleeding may be from the mouth, nose and stomach, which leads to blood in vomit and poo.

The majority of patients who experience bleeding die in a short space of time so it is essential to seek help as soon as possible.

What's going to help?

If you plan to travel abroad you should always speak to your doctor about any vaccinations you need to have before travelling.

For more help and information

• The NHS Choices website can provide you with more information on yellow fever
• You can get more information on the yellow fever vaccination from your GP or from the Department of Health

Last reviewed by Great Ormond Street Hospital: 28 January 2010

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