Yellow fever
Published by Bupa's health information team, February 2009.
This factsheet is for people who have yellow fever, or who would like information about it.
Yellow fever is a tropical virus. You get it from being bitten by infected mosquitoes. Yellow fever mainly occurs in sub-Saharan Africa and tropical areas of South America.
It's estimated that every year 200,000 people worldwide are infected with yellow fever and 30,000 people die as a result. However, the number of cases may actually be much higher. This is because in more remote areas the disease is often not reported.
- About yellow fever
- Symptoms of yellow fever
- Causes of yellow fever
- Diagnosis of yellow fever
- Treatment for yellow fever
- Prevention of yellow fever
- Further information
- Questions and answers
- Related topics
- Sources
About yellow fever
Yellow fever is caused by a flavivirus. Flaviviruses cause a range of human infections and many of these are transmitted by mosquitoes and ticks, including dengue fever, Japanese encephalitis and yellow fever. Hepatitis C is also in the flavivirus family.
Yellow fever is one of the most lethal viral diseases and is spread by infected mosquitoes. It's an arbovirus (arthropod-borne virus) infection. You are at risk of getting the disease if you travel into areas where they are present. In parts of sub-Saharan Africa and tropical areas of South America the virus is constantly present with low levels of infection.
Preventive measures are essential to protect yourself and stop the spread of yellow fever. You can do this by getting vaccinated against the disease and protecting yourself against mosquito bites.
Symptoms of yellow fever
You usually get symptoms three to six days after you have been bitten by an infected mosquito. This is known as the incubation period. The symptoms usually come on suddenly and can include:
- high fever (39 to 40 °C)
- shivers
- headaches
- nausea and/or vomiting
- loss of appetite
- muscle pain and aches
- bloodshot eyes
- flushing of your face
These symptoms usually last for three to four days and represent the acute phase of the virus. Most people begin to recover after this phase and their symptoms gradually disappear.
However, within 24 hours of seeming to recover, 15 to 25 percent of people enter a toxic phase of the disease. Symptoms during this phase are far more serious and may be life-threatening, including:
- fever
- jaundice (yellowing of your skin and the whites of your eyes) - this is where the disease gets its name
- kidney failure, which may result in you no longer being able to pass urine
- stomach pain with vomiting
- blood in your vomit or stools
- bleeding from your mouth, nose or eyes
Up to half of people who enter the toxic phase of the disease die within 10 to 14 days. Major organ failure, shock, delirium and coma usually occur before death. The rest of the people who enter this phase usually make a full recovery.
Causes of yellow fever
Yellow fever is transmitted by bites from infected mosquitoes in humans and monkeys. The infection is spread by certain species of biting mosquitoes, including Aedes, Sabethes and Haemogogus mosquitoes (South America only). The virus can only be spread in countries where these mosquitoes live.
There are three main ways in which the virus is transmitted: jungle, intermediate and urban. These are often referred to as transmission cycles.
Jungle yellow fever
In tropical rainforests, yellow fever occurs in monkeys who have been bitten by forest mosquitoes. When humans enter the forest, for example to work, the virus can be passed on through a bite from an infected forest mosquito.
Intermediate yellow fever
It's possible for mosquitoes to infect both animals and humans. Intermediate yellow fever transmission only happens in moist savannah zones of Africa, and can cause small epidemics in rural villages.
Urban yellow fever
If a person, infected with yellow fever in the jungle, returns to an urban area and is bitten by an Aedes mosquito, the mosquito will become infected. This mosquito may then go on to bite other humans spreading the virus from person to person. This is how outbreaks of yellow fever start in built-up areas, and has resulted in widespread epidemics in the past.
Diagnosis of yellow fever
It's important to see a doctor and get a diagnosis if you have suspected yellow fever. If you're abroad, you should go to a local hospital or see a doctor for a diagnosis. If you're in the UK, you should see your GP.
Your GP or doctor will ask you about your symptoms and ask you to take a blood test. The blood test will confirm whether or not you have yellow fever.
Yellow fever can be difficult to recognise, especially in the acute phase of the disease. It can be easily confused with other diseases such as malaria, typhoid and dengue fever. It's important to get an accurate diagnosis so that you can be given appropriate care.
Treatment for yellow fever
There is no specific treatment for yellow fever, other than preventive measures.
Some of your symptoms may be relieved through bed rest and taking rehydration salts and paracetamol. Always read the patient information leaflet that comes with your medicine.
Intensive hospital care may help people who enter the toxic phase of the disease. However, this type of hospital care is often not available in poorer countries where the virus is widespread.
People who recover from the disease will be immune to the virus for the rest of their life.
Prevention of yellow fever
Prevention is vital in protecting yourself and stopping the spread of yellow fever. Current preventive measures include immunisation and protecting yourself from mosquito bites.
Immunisation
A highly effective and safe vaccine is available for yellow fever. The vaccine is given as a single dose injection. The protective effect (immunity) happens within one week of having the injection for 95 percent of people. The vaccine gives protection for at least 10 years, possibly the rest of your life. However, after 10 years you will need to have a booster vaccination.
If you're planning to go to areas where there is yellow fever infection, you should be vaccinated at least 10 days before you travel. You can get vaccinated at a recognised vaccination centre. To find your nearest Vaccination Centre go to the National Travel Health Network and Centre website (see further information). You will be given an International Certificate of Vaccination or Prophylaxis (ICVP) which becomes valid 10 days after your injection and will need updating every 10 years.
When travelling to some places, you may be asked to show an ICVP before you are allowed to enter the country. This is often the case when travelling from Africa or South America to Asia. This is because there are no reported outbreaks of yellow fever in Asia, despite the presence of the Aedes mosquito. If an infected person were to enter Asia and be bitten by an Aedes mosquito, the virus could become widespread.
Protection from mosquito bites
Most mosquitoes are active between dusk and dawn, but the mosquitoes that spread the yellow fever virus are active during the daytime. To protect yourself against being bitten, try the following.
- Don't go into areas that are infested with mosquitoes, especially at times when they are active.
- Use DEET insect repellent on exposed areas of skin and make sure you re-apply it at regular intervals.
- Wear loose fitting clothing (mosquitoes can bite through tight clothing).
- If you're staying in basic accommodation with no air-conditioning or screens, make sure you use a mosquito net over your bed.
- Use an insect spray in your room before going to bed, or use a plug-in insecticide.
Further information
- National Travel Health Network and Centre (NaThNaC)
www.nathnac.org
Related topics
Sources
- Eddleston M, Davidson R, Wilkinson R, et al. Oxford handbook of tropical medicine. 2nd ed. Oxford: Oxford University Press, 2006:238-241
- Yellow fever. World Health Organisation. www.who.int, accessed 13 October 2008
- Yellow fever. National Travel Health Network and Centre. www.nathnac.org, accessed 13 October 2008
- Yellow fever. GP Notebook. www.gpnotebook.co.uk, accessed 13 October 2008
- Immunisation against infectious disease 2006 - The Green Book Department of Health. www.dh.gov.uk, accessed 13 October 2008
- Insect Bite Avoidance. National Travel Health Network and Centre. www.nathnac.org, accessed 15 October 2008
This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
Publication date: February 2009
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