
The World Health Organization said on Friday that at least 1,500 people had potentially been exposed to the deadly Ebola virus in the Democratic Republic of Congo's North Kivu region, where fear of local militia is preventing aid workers from reaching some areas.

But it expected more people to become infected and could not be sure that it had identified all chains by which the virus is spreading in the eastern part of the country beset by militia violence.

The region is haunted in particular by the Allied Defence Forces, a Ugandan Islamist rebel group blamed for hundreds of civilian deaths over the past four years.

An Ebola patient is being checked by two medical workers after being admitted into a Biosecure Emergency care Unite (CUBE) in Beni, Democratic Republic of Congo

An Ebola patient is lead by two medical workers into CUBE, which has being constructed by The Alliance for International Medical Action in response to the Ebola outbreak

Emergency: A health worker gets ready to perform medical checks inside an Ebola Treatment Centre run by The Alliance for International Medical Action (ALIMA) in Beni

More than 500 people including health workers have been vaccinated against the disease in Congo's latest outbreak, marked by a total of 78 confirmed and probable cases, including 44 deaths, the WHO said.

Some 1,500 people have been identified as contacts of people infected with the disease that causes fever, vomiting and diarrhoea.

'We don't know if we are having all transmission chains identified. We expect to see more cases as a result of earlier infections and these infections developing into illness,' WHO spokesman Tarik Jasarevic told a Geneva news briefing.

'We still don't have a full epidemiological picture... The worst case scenario is that we have these security blindspots where the epidemic could take hold that we don't know about,' he said.

A health worker gets ready to perform checks at an Ebola treatment centre in Beni

An Ebola patient is lifted up by two medical workers after being admitted into a Biosecure Emergency care Unite

On August 1, Beni declared an outbreak of Ebola epicentered in Mangina - a small town that had been a relative haven from the fighting - where six members of the same family died of the disease.

In the Beni region, in the Democratic Republic of Congo's eastern province of Kivu, the twin peril has bred fear and despair

'I fled here from Kokola, where the ADF were committing atrocities,' said Pascaline Fitina, a 36-year-old woman, sitting alone, her head in her hands.

'I went to my elder sister, but she has died of Ebola and her husband is being quarantined at the treatment centre. I don't what to do.'

Pascal Lukula, a 38-year-old farmer with five children, said he was stuck in Mangina, unable to get to other members of his family, because of the encroaching militia.

'We are caught between the hammer and the anvil,' he sighed. 'The ADF's on one side, and Ebola on the other.'

The outbreak - the country's 10th since the disease was discovered in then-Zaire in 1976 - was announced just a week after the end of an Ebola flareup in northwestern Equateur province that claimed 33 lives.

The infected will be treated in 10 Biosecure Emergency care Units (CUBEs), which will be used for the first time to treat Ebola patients and are currently being constructed by The Alliance for International Medical Action in response to the outbreak.

An unconfirmed Ebola patient is lead by two medical workers to his new ward in a Ebola Treatment Centre

Medical workers at a special treatment centre in Beni disinfect the coffin of a suspected Ebola fatality

Ebola causes serious illness including vomiting, diarrhoea and in some cases internal and external bleeding. It is often fatal if untreated.

The disease is caused by a virus that is transmitted to people from wild animals and spreads among humans through close contact with the blood, body fluids, secretions or organs of an infected person.

In Mangina, located 30km (18 miles) southwest of the city of Beni, suspicion and rumour seem to have spread across the population.

Containers of chlorinated water have been installed in front of all shops and in the markets to provide rudimentary hand protection.

'I wear gloves to protect me from the epidemic,' said Jonas Mumbere, 26, who drives a motorcycle taxi.

'Customers have started to think twice about getting on the motorbike for fear of contamination.'

Elodie Zena, a 28-year-old sex worker, said: 'Business has dropped off - customers are afraid. I've heard that even the sweat of someone who is infected can contaminate us. I've got two children and I don't how I can feed them.'

Health experts have long fretted about the problems of combating Ebola in the DRC, a vast country that is poor and unstable and shares boundaries with nine countries.

Three medical workers check on an Ebola patient in a Biosecure Emergency care Unite

On Tuesday, the World Health Organization chief, Tedros Adhanom Ghebreyesus, also warned that conflict had helped create 'a conducive environment for the transmission' of Ebola.

Hanna Leskinen of the International Committee of the Red Cross said the grassroots work in combating Ebola lies in locating and treating patients and isolating people who have been in contact with them.

In North Kivu, 'people are moving around all the time, fleeing the latest wave of violence,' she said. 'It enormously complicates search and followup of infected people.'

Another worry is for the safety of health workers - 'the police and army are providing night-and-day security' for them, said North Kivu's governor, Ephrem Kasereka.