FACTBOX: What do we know about the Ebola outbreak in Congo and Uganda?

The World Health Organization on Sunday declared an Ebola outbreak in the Democratic Republic of Congo and Uganda to be a public health emergency of international concern.

The WHO said the outbreak, caused by the Bundibugyo strain of the virus, does not meet the criteria of a pandemic emergency but that countries sharing land borders with the DRC are at high risk for further spread.

What do we know about this new Ebola outbreak and how it has spread?

WHAT IS EBOLA?

Ebola disease is a severe, often-fatal virus, which causes fever, body aches, vomiting and diarrhoea, and spreads through direct contact with the bodily fluids of infected persons, contaminated materials or persons who have died from the disease, according to the Africa Centres for Disease Control and Prevention.

This is the Democratic Republic of Congo's (DRC) 17th outbreak since its discovery in 1976.

WHAT IS THE BUNDIBUGYO STRAIN?

Bundibugyo is a strain of the virus. According to the WHO, there have been two previous outbreaks of the strain.

The outbreak is "extraordinary" as there are no approved Bundibugyo virus-specific therapeutics or vaccines, unlike for Ebola-Zaire strains, it said.

"Unfortunately, Bundibugyo has fewer proven countermeasures than Zaire ebolavirus, where vaccines have been highly effective in controlling outbreaks," said Amanda Rojek, Associate Professor of Health Emergencies, Pandemic Sciences Institute at the University of Oxford, in a statement.

WHICH COUNTRIES HAS IT SPREAD TO?

The governments of the Democratic Republic of Congo (DRC) and Uganda have confirmed cases, with the outbreak most severely affecting the DRC.

The Africa Centres for Disease Control and Prevention said on Sunday it was coordinating with South Sudan to monitor cross-border activity and limit further international spread.

HOW MANY PEOPLE HAVE BEEN AFFECTED?

The WHO said on Sunday that eight lab-confirmed cases were recorded, 80 suspected deaths and 246 suspected infections.

Another case in Goma, the eastern DRC town controlled by M23 rebels, was confirmed in a statement released by them on Sunday.

Ugandan officials also confirmed a second case on Sunday.

The WHO, however, warned that "there are significant uncertainties to the true number of infected persons and geographic spread associated with this event at the present time".

-Reporting by Kopano Gumbi in Johannesburg;Editing by Peter Graff/Reuters