Yellow fever is a serious viral infection that is spread by certain types of mosquito. It’s mainly found in sub-Saharan Africa, South America and parts of the Caribbean.
The virus that causes yellow fever is passed to humans through the bites of infected mosquitoes. The mosquitoes that spread the infection are usually active and bite during daylight hours, and are found in both urban and rural areas.
Yellow fever can’t be passed directly from person to person through close contact.

The symptoms of yellow fever occur in two stages. The initial symptoms develop three to six days after infection, and can include:
• a high temperature (fever)
• a headache
• nausea or vomiting
• muscle pain, including backache
• loss of appetite
This stage will usually pass after three to four days and most people will make a full recovery.
However, around 15% of people go on to develop more serious problems, including jaundice (yellowing of the skin and whites of the eyes), kidney failure and bleeding from the mouth, nose, eyes or stomach (causing blood in your vomit and stools).
Up to half of those who experience these symptoms will die.

The vaccination against yellow fever should be given at least 10 days before travelling to an area where the infection is found, to allow your body to develop protection against the virus that causes the infection.
Some countries require a proof of vaccination certificate before they will let you enter the country. This will only become valid 10 days after you are vaccinated.