Vaccine fears over Congo Ebola outbreak

It may be impossible to use a vaccine to tackle Democratic Republic of Congo's new Ebola outbreak that has caused four confirmed cases, including two health workers, a senior World Health Organisation (WHO) official has warned.

Officials have not confirmed the particular strain of Ebola causing the outbreak, which may have killed 20 people, but WHO's emergency response chief Peter Salama said it could be the Zaire, Sudan or Bundibugyo strain.

If it is the Zaire strain, the Merck vaccine used in the last Ebola outbreak may be an option, otherwise the situation will be much more complex "and we may not have any vaccine options", Salama told Reuters at WHO's headquarters in Geneva on Thursday.

"The majority of the cases occurred in the second half of July ... When the provincial medical teams have looked back ... they have noted cases that could be consistent with Ebola that began even in May but it's far too early to say," Salama said.

"It would appear that the risk, as we can surmise for DRC, is high. For the region it's high given the proximity to borders, particularly Uganda.

"We're talking about a few health areas mostly in one health zone. So we are talking about tens of kilometres but I stress that this is very preliminary information at this stage."

International experts set up a laboratory on Thursday in the city of Beni, 30 km from where the outbreak was declared, WHO and Congolese officials said.

Officials from the United Nations, World Bank, WHO Congo's Ministry of Health, including Health Minister Oly Ilunga, will support a team already on the ground.

Congo declared the outbreak on Wednesday, just days after another that killed 33 people in the northwest was declared over.

The 20 died in and around Mangina, a densely populated town in North Kivu province about 30 km southwest of the city of Beni and 100 km from the Ugandan border.

The ministry has not made public when the deaths occurred. Another six who are still living are showing signs of fever, of which four tested positive.

"The Government-Partner delegation is holding its first meeting to organise the response," North Kivu governor Julien Paluku tweeted.

"Already a ... team from Kinshasa is installing a laboratory and a single coordination centre."

"The response is already in place," David Gressly, United Nations Deputy Special Representative Congo, told reporters in Beni.

"We (the UN mission) will offer logistical support and if needed security support. We are all ... here to see how we can organise this as fast as possible."

Australian Associated Press