Ebola vaccinations are set to begin in the two rural areas of the Democratic Republic of Congo where the latest deadly outbreak was declared this month, with the number of confirmed cases having risen to 35, including 10 deaths.

A vaccination campaign is already under way in Mbandaka, a city on the Congo River where four Ebola cases have been confirmed. About 100 health workers have been vaccinated there as frontline workers face high risk from the virus, which is spread via contact with bodily fluids of those infected, including the dead.

The vaccination campaign will begin on Monday in the rural areas of Bikoro and Iboko in the country’s northwest, health ministry spokeswoman Jessica Ilunga said.

“The health minister can be found at this moment in Bikoro assessing the preparations for the vaccination campaign,” Ms Ilunga said.

Of the 10 confirmed Ebola deaths, five have occurred in Bikoro, two in Iboko and three in the Wangata area of Mbandaka. In addition to the confirmed Ebola cases there are also 13 probable cases and six suspected ones, the health ministry said.

The World Health Organisation (WHO) emergencies chief has said the next few weeks are crucial in determining whether the outbreak can be brought under control. Complicating factors include the spread of Ebola to a major city, the fact that health workers have been infected and the existence of three or four “separate epicentres” that make finding and monitoring contacts of infected people more difficult.

Simon Calder on how ebola outbreak in Democratic Republic of Congo affects travellers

WHO director-general Tedros Adhanom Ghebreyesus told a meeting in Geneva on Saturday: “I am personally committed to ensuring that we do everything we can to stop this outbreak as soon as possible.”

This is Congo’s ninth Ebola outbreak since 1976, when the haemorrhagic fever was first identified.

There is no specific treatment for Ebola. Symptoms include fever, vomiting, diarrhoea, muscle pain and at times internal and external bleeding. The virus can be fatal in up to 90 per cent of cases, depending on the strain.

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The WHO is using a “ring vaccination” approach, targeting the contacts of people infected or suspected of infection and then the contacts of those people. More than 600 contacts have been identified.

The organisation is also accelerating efforts with nine neighbouring countries to try to prevent the Ebola outbreak from spreading there, saying the regional risk is high. It has warned against international travel and promoted trade restrictions.

The difficulties in keeping track of contacts was highlighted by the fact that two Ebola patients were taken from a treatment centre in Mbandaka earlier this week with the help of their families, according to aid agency Médecins Sans Frontières, known in the US as Doctors Without Borders.

One of the patients died at home, and his body was returned to the hospital, while the second came back to the facility the next day but later died.