Médecins Sans Frontières (MSF) is taking part in a vaccination campaign targeting 525,000 people in response to an outbreak of yellow fever in Sierra Leone. The five-day campaign started on January 10.

Thirty-five MSF-led vaccination teams of around 10 people each are now working in and around Bo, the second largest city in the country.

Two cases of yellow fever have been confirmed in Sierra Leone in recent months and were treated at the MSF supported hospital outside Bo. The disease, which is spread by mosquitoes, is so serious that even one confirmed case of the illness is sufficient to call for a mass vaccination campaign.

In response to the outbreak, the Sierra Leonean health authorities have decided to vaccinate the entire population of Bo district, which has approximately 525,000 inhabitants. MSF is responsible for targeting 225,000 people, in close cooperation with the Ministry of Health, which is also carrying out the remaining vaccinations.

"Those who are infected with yellow fever have a high likelihood of dying and, because many people in the area are not vaccinated against the disease, it is important to quickly reach and vaccinate as many people as possible in the area to prevent the disease from spreading," said Johan Mast, Head of Mission for MSF in Sierra Leone.

There is no specific treatment available for yellow fever and the only option is to treat the symptoms that include fever, jaundice and haemorrhages. For those with the most severe form of the disease, about 50 percent die, and the World Health Organisation estimates that yellow fever kills 30,000 people every year, mainly in Africa. Outbreaks of the disease can be prevented and controlled by mass vaccination campaigns targeting all adults, with the exception of pregnant women, as well as children over nine months old.

Last week, MSF teams started extensive communication activities to inform people in the district about the campaign and the importance of getting vaccinated.

"We have had cars with speakers travelling around, posters in the villages and at health centres and jingles on the radio to let people know about the campaign," said Vikki Stienen, MSF's emergency coordinator in Bo. "We also have health promoters using megaphones and have held meetings with local leaders, teachers, and local government officials".

Yellow fever is endemic in Sierra Leone and routine immunizations only started in 2002, targeting babies between 9-12 months old but leaving the majority of the population unprotected against the virus.