Ugandan officials had previously said the patient in Nigeria had travelled to eastern DR Congo, only transiting through Uganda. On Sunday, however, the health ministry said Uganda and Nigeria were both working to establish her movements, complete travel history and possible routes of exposure.

The Ugandan health minister said the recent cases meant the risk had not ended and further underscored the need to "remain vigilant".

"We share a border with [DR Congo], where transmission continues, and our communities remain closely connected through trade, travel and family ties," Baryomunsi said.

The disease spreads from one person to another by contact with infected bodily fluids such as blood or vomit.

The Bundibugyo species of Ebola behind this outbreak is relatively rare and there is still no vaccine or specific treatment - though trials are under way.

Additional reporting by Swaibu Ibrahim in Kampala

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