The Marburg virus causes death within 48 hours.

Its symptoms include high fever, headaches, vomiting and bleeding from the gums and skin.

Like Ebola, to which it is related, it is incurable and does not respond to treatment.

The virus has struck mainly gold miners in the remote northeastern part of DCR and is thought to be spread by bats and rats.

Ugandan officials fear the virus could spread over the border into areas which are more densely populated.

Trade routes

"An alert has been sent to all districts neightbouring the DCR and southern Sudan," said Francis Omaswa, the government's director general of health services.

Trade routes between Uganda and DCR have been open since last year when Ugandan troops went into DCR to back rebels opposed to the country's president, Laurent Kabila.

Northeastern DCR is controlled by the rebels, but they have agreed to co-operate with government health officials to investigate the disease.

An international task force, including Ugandan doctors, has been sent to the area.

The World Health Organisation (WHO) confirmed earlier this week that the Marburg virus was behind the deaths.

The diagnosis was made from blood samples taken from the victims and tested by the National Institute of Virology in South Africa.

Victims bleed to death

Because of the similarities with Ebola, there was speculation that it was to blame for the deaths.

Ebola was first identified in the 1970s and its worst outbreak was in DCR, then Zaire, in 1995 when it killed 350 people.

Congolese Health Minister Mashaka Mamba has said it is possible the DCR epidemic is tailing off.

The WHO is still trying to trace the exact source of the outbreak.

The Marburg virus was first identified in 1967, in the North German town of Marburg, after a laboratory worker who was taking blood from African monkeys became ill and died.

Even in the best hospitals, with the most modern facilities, the virus can be expected to kill a quarter of those who go down with it.