This is Congo's 10th Ebola outbreak, but it is the first in the densely forested hillside provinces of North Kivu and Ituri, where militia-led violence and ethnic killing have undermined security in certain areas for decades.
The widening geographic spread of the virus, and its presence in yet another zone under the sway of armed groups, raises the risk of it spreading out of control, even while the technical tools to rein it in are better than ever.
The virus derives its name from the 250-km long Ebola river which flows through Congo and at a point is over 60-km from Yambuku, the rural Congolese area where some of the first patients of the disease were reported.
This is the fifth such declaration in history. Previous emergencies were declared for the devastating 2014-16 Ebola outbreak in West Africa that killed more than 11,000 people, the emergence of Zika in the Americas, the swine flu pandemic and polio eradication.
The patient was a priest who became infected during a visit to the town of Butembo, 200 km (124 miles) north of Goma, where he interacted with Ebola patients, Congo's health ministry said in a statement.
The treatments approved for shipment to Uganda were Mapp Biopharmaceutical's ZMapp, Regeneron Pharmaceuticals Inc's Regeneron and Remdesivir, made by Gilead Sciences , said WHO spokesman Tarik Jasarevic.
Congo's epidemic is the second worst ever, with 2,108 cases of Ebola and 1,411 deaths since last August. This week it reached Uganda, where three cases were recorded, all in people who had arrived from Congo. Two of them died.
Health experts agree the experimental Ebola vaccine has saved multitudes in Congo, but after nearly a year and some 171,000 doses given, the epidemic shows few signs of waning - over 1700 have died from the disease.
In the Top frames this week The Nobel Peace Prize 2014 was awarded jointly to Kailash Satyarthi and Malala Yousafzai "for their struggle against the suppression of children and young people and for the right of all children to education".