BENI, Congo -- Congo's latest deadly Ebola outbreak has spread into a neighbouring province, the health ministry said Tuesday, as health workers began using an experimental treatment for the disease.

Health officials are hoping the mAb114 therapy, isolated from a survivor of an Ebola outbreak in 1995, will be effective in this outbreak that so far has 30 confirmed cases including 14 deaths.

Five patients have been given the treatment, said the World Health Organization's director-general, Dr. Tedros Adhanom Ghebreyesus. Four other experimental treatments have been approved for use, he said.

The outbreak spread from North Kivu province into neighbouring Ituri province in Congo's turbulent northeast when a man who had been treated for heart problems in Mangina, where the outbreak was declared Aug. 1, returned home, the health ministry said. He has since died and tests confirmed he had Ebola.

Vaccinations began last week in Mangina and Beni, the major town about 30 kilometres (18 miles) away where Ebola treatment centres have been set up. Health authorities are using what is called a ring vaccination technique in which health workers are vaccinated first, along with contacts of Ebola patients and their contacts.

Seven of the nearly 75 health workers in Mangina have been infected, Tedros said. More than 200 health workers have been vaccinated, along with 20 residents in the Beni region, he said. There are 3,000 vaccine doses in Congo.

The work to contain Ebola is challenged by the presence of several armed groups in the densely populated region close to the Ugandan border. WHO has called for secure access to all affected populations and for the cessation of hostilities.

"The virus is dangerous to us all," Tedros said.

There are designated "red zones" where health workers cannot go because of the insecurity, raising concerns that cases could easily spread there, he said.

"We are on an epidemiological precipice," WHO's emergency preparedness chief, Dr. Peter Salama, said in a Twitter post, with a limited window of opportunity to stop the outbreak from spreading into those areas.

For now the epicenter of the outbreak is in and around Beni so aid workers have been able to move with relative safety, said Jean-Philippe Marcoux, Congo country director for Mercy Corps.

The area around Mangina and Beni, however, is "almost completely surrounded by armed groups," the International Committee of the Red Cross said in a statement.

North Kivu is densely populated with more than 1 million displaced people, and while this is Congo's tenth Ebola outbreak health officials have said the local population is not familiar with the disease. That makes outreach more challenging.

"The unknown can create more fear," Marcoux said.

The WHO chief said the risk of international spread is low. He said officials have been in contact with neighbouring Uganda, Rwanda, Burundi and South Sudan.

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Petesch reported from Dakar, Senegal.