The strain, for which there is no approved vaccine or treatment, was declared an emergency of international concern by the WHO on Sunday.
WHO Chief Tedros Ghebreyesus told reporters: "We are now revising our risk assessment to very high at the national level, high at the regional level, and low at global level."
So far, 82 cases have been confirmed in Congo, with seven confirmed deaths, 177 suspected deaths and almost 750 suspected cases.
The situation in Uganda is stable, with two cases confirmed in people who travelled from the DRC, one of them fatal, Tedros said.
Mahamud, WHO Director of Health Emergency Alert & Response Operations said the potential of this virus spreading rapidly is high, very high, and that changed the whole dynamic.
