If you're going to Africa or South America you may be a risk of contracting yellow fever.
Yellow fever is a mosquito-borne virus that was largely eradicated back in the 80’s and 90’s. However, in recent years it has re-emerged as a threat in a number of countries in Africa and Latin America. This guide looks at what yellow fever is, where it’s located, how deadly it is and what is being done to control its spread.
What is yellow fever and where is it found?
Yellow fever is a virus spread by mosquitoes that can cause serious illness and death. It's known as yellow fever because of the jaundiced appearance of the skin experienced by sufferers. It occurs primarily in 31 African and 13 Latin American countries, where conditions are best suited to transmission of the virus (e.g the presence of the right type of mosquitoes, monkeys and high human populations).
African countries where yellow fever is endemic include:
- Burkina Faso
- Central African Republic
- Republic of Congo,
- Republic of Cote d'Ivoire
- Democratic Republic of Congo
- Equatorial Guinea
- Sierra Leone
- South Sudan
Latin American countries where yellow fever is also endemic include:
- French Guiana
- Trinidad and Tobago (Trinidad only)
Yellow fever symptoms
Yellow fever doesn’t kill everyone who is infected. In the majority of cases, those infected experience no symptoms at all or recover from their symptoms after a short period of illness. However, 15% of people go on to develop much more serious symptoms that can result in organ damage and death. There are three main phases in the infection cycle:
- The acute phase. After incubating for three to six days, the virus attacks the body causing a range of symptoms including fever, muscle pain, backache, headache, loss of appetite, nausea and vomiting. It's difficult to diagnose at this stage as the symptoms are similar to malaria, dengue fever, leptospirosis, viral hepatitis, haemorrhagic fever and even poisoning.
- The remission phase. After three to four days these symptoms disappear and it's at this stage that most people recover from their illness. But for the 15% who don’t, the remission phase can be as short as 24 hours before they go on to develop much more serious problems.
- The toxic phase. The toxic phase is the final phase, where the fever returns along with jaundice, abdominal pain, vomiting, bleeding from the eyes, nose or mouth, seizures, delirium and coma. Half of this group die within 10 to 14 days as a result of serious organ damage including kidney deterioration, while the other half will recover without significant damage.
How do you get yellow fever?
Yellow fever is transmitted by infected mosquitoes, mainly by the Aedes and Haemagogus mosquito species. There are three main types of transmission:
- Sylvatic (or jungle) yellow fever. Wild mosquitoes infected by the virus feed on monkeys in the jungle, spreading the virus to other monkeys and to any humans who enter the jungle.
- Intermediate (savannah) yellow fever. Semi-domestic mosquitoes infect monkeys and humans in villages bordering jungle and rainforest areas.
- Urban yellow fever. Infected humans introduce the virus into high population areas where domestic mosquitoes are present and the virus is then passed from human to human.
What can you do to lessen your chances of contracting yellow fever?
There is no treatment for yellow fever other than hospital care, so prevention is vital for those most at risk. Measures that can reduce the likelihood of contracting the virus include:
- Vaccination. This is the first line of defence and once vaccinated, a person remains immune from yellow fever for life. People travelling to or from countries where the virus is endemic should be vaccinated or have a certificate showing they have been vaccinated previously.
- Mosquito control. While it's not possible to control wild mosquito populations in jungle areas, the use of insecticides and the elimination of potential breeding sites can reduce mosquito numbers in urban areas.
- Mosquito avoidance. The use of mosquito netting, screens, insect repellent and full length clothing can all help to reduce your likelihood of being bitten.
- Rapid response. Prompt detection of yellow fever and a timely response through emergency vaccination campaigns can control outbreaks and reduce infection numbers.
- Long-term planning. Mass immunisation programs in at-risk countries are the best means of control, but these are hampered by lack of money, under-reporting of cases and shortages of vaccine (which takes around six months to produce).
Should you get your vaccinations?
Vaccination is the number one measure for preventing yellow fever. For those living in high risk areas, vaccination programs where children are immunised from the age of nine months are the ideal goal, but not yet a reality in many developing countries.
For those travelling to or from high risk areas, vaccination is highly recommended and is often required as a condition of travel. Vaccination is affordable and safe, with few cases of serious side effects being reported and provides immunity from yellow fever within 10-30 days.
The only instances where vaccination is not recommended are:
- For children under nine months and adults over 60
- People allergic to the egg protein used in the vaccine
- Pregnant or breastfeeding women
- Those with immune deficiencies such as from HIV
Even in these cases, vaccination should be considered as part of a risk-benefit assessment, because the risk of death from yellow fever is much greater than any risks related to the vaccine.
You may be interested to know that:
- There are between 84,000 and 170,000 cases of yellow fever every year and up to 60,000 deaths
- While largely confined to Africa and Latin America these days, in the 17th to 19th centuries, yellow fever outbreaks were reported in North America, Europe and the UK
- Since the launch of Yellow Fever Initiative in 2006 (a mass vaccination program led by WHO and UNICEF), the number of yellow fever cases has been steadily decreasing
- A single dose of vaccine will give sustained immunity and life-long protection against yellow fever and a booster dose is not required in most cases
- The vaccine provides effective immunity within 10 days for over 90% of people and within 30 days for 99% of people
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