Yellow Fever is spread by mosquitoes and is found in tropical parts of Africa and South America. Some countries require proof of yellow fever vaccination in the form of an International Certificate of Vaccination before they allow a traveller to enter. Failure to provide a valid certificate can lead to a traveller being quarantined, immunised or denied entry.

What is Yellow fever?
Yellow fever is a serious, sometimes lethal, viral diseases spread through the bite of an infected mosquito. It occurs in both jungle and urban environments and is particularly prevalent in the rainy season.

Yellow fever has an incubation period of 3 to 6 days and first phase is characterised by fever, muscle pain, headache, shivers, loss of appetite, nausea and vomiting. After 3 to 4 days most patients improve and their symptoms disappear. However, within 24 hours of apparent recovery, 15-25% of patients progress to a more serious illness involving jaundice, haemorrhagic fever and deterioration of kidney function. 20% to 50% of patients who develop this form of the disease die within 7-10 days after the onset.

Where is Yellow fever a problem?
Yellow fever occurs in tropical parts of South America and sub-Saharan Africa, most commonly West Africa. There is no risk of transmission in the UK from imported cases since the mosquito vector does not occur in the UK.

Nearly all affected countries require proof of yellow fever vaccination in the form of a Certificate of Vaccination. Failure to provide a valid certificate to port health authorities can result in travellers being quarantined, immunised or denied entry.

Who is at risk?
Although ongoing cases and outbreaks are occurring in Africa and South America, the disease is preventable by vaccination and remains a very rare cause of illness in travellers. Risk of acquiring yellow fever is determined by immunisation status, travel destination, intensity of yellow fever transmission in area to be visited, season of travel, duration of travel and activities allowing exposure to mosquitoes.