Yellow fever is a severe viral infection carried by mosquitoes. It is a common infection in most of sub-Saharan Africa and South American countries, and parts of Central America and the Caribbean. There is currently no cure for yellow fever, and severe cases can be fatal, so it is important to protect yourself in advance of travel to these areas.
Mosquitoes belonging to the Aedes and Haemagogus species, which can live and breed domestically, in the wild, or both carry yellow fever. For this reason, there are three types of transmission cycles:
Sylvatic yellow fever, or jungle yellow fever, is usually carried by mosquitoes between monkeys, who are the primary reservoir of yellow fever. Humans travelling through forested areas may be bitten by an infected mosquito and contract yellow fever.
Semi-domestic mosquitoes that bite both monkeys and people transmit intermediate yellow fever. This type of yellow fever is the most common type of outbreak in Africa.
Urban yellow fever tends to result in a large epidemic. Infected people introduce the virus into densely populated areas with a high density of mosquitoes. In this instance, the population has very little immunity to yellow fever due to lack of prior exposure, and the virus is quickly carried from human to human by mosquitoes.
If you are travelling to any areas where the virus is prevalent, getting vaccinated against yellow fever is highly recommended. The vaccine is available from registered yellow fever vaccination centres and costs around £60-80. It should be administered at least ten days before travel and provides lifelong immunity to the virus.
A small proportion of people experience side effects of the vaccination, which can include:
Swelling, bruising or pain around the site of injection
Nausea, vomiting or diarrhoea
If you experience symptoms of allergy to the vaccination, including a skin rash, difficulty breathing or loss of consciousness, you should seek medical help immediately.
Even if you are vaccinated against yellow fever, you should take precautions to avoid being bitten by mosquitoes in high-risk areas. Click here for advice on avoiding mosquito bites.
Yellow fever has an incubation period of three to six days, and symptoms can take up to a week to present itself. Many people do not experience any symptoms at all. Those that do usually recover within three to four days. Early signs of yellow fever include:
High temperature (over 38C)
Muscle pain and backache
Loss of appetite
Nausea and vomiting
A small percentage of patients enter a more toxic phase within 24 hours of recovering from the initial symptoms. This toxic phase indicates that several body systems are being affected, usually the liver and the kidneys. The ‘yellow’ in yellow fever refers to the tendency to develop jaundice at this stage, apparent in the yellowing of the skin and eyes. Other symptoms of severe yellow fever can include dark urine, abdominal pain, and bleeding from the mouth, nose, eyes or stomach.
At the toxic phase, yellow fever is fatal in 50% of patients. It is vital to seek medical help if you experience any of the symptoms of early yellow fever while travelling in an area where the infection is prevalent. If you experience any new symptoms after returning from your trip, seek consultation from a doctor immediately.
Although there is no cure for yellow fever, symptoms can be treated while the body fights off the infection. Painkillers such as ibuprofen or paracetamol can relieve pain and lower your temperature, while drinking plenty of fluids will help you avoid dehydration. Most people recover after three or four days. More severe symptoms will need immediate treatment in the hospital.
NHS - Yellow Fever: https://www.nhs.uk/conditions/yellow-fever/