The wife and daughter of a man who died from Ebola last week have been diagnosed with the disease, causing panic among DR Congo officials.
It marks the first transmission of the disease in the city of Goma on the Rwandan border – something health experts have long feared.
They have begun the long work of vaccinating anyone who may have come into contact with the man.
He died on Wednesday after spending several days at home with his large family while showing symptoms of Ebola.
Officials say the man’s entire family was at “high risk”, adding it was likely that others have contracted the disease.
DR Congo is grappling with the world’s second largest Ebola epidemic on record, which has claimed more than 1,800 lives since the outbreak was declared a year ago today.
Rwanda’s state minister for foreign affairs, Olivier Nduhungirehe, announced that the border with DR Congo had closed – only a day after being praised by the World Health Organisation (WHO) for keeping it open.
DR Congo’s presidency condemned the move, shortly before confirming the border had re-opened.
The Rwandan health ministry has advised against unnecessary travel to the area.
Despite saying the regional spread is “very high”, the WHO has recommended against travel restrictions in the area, adding that border closures would push people to unofficial immigration posts.
The man who died last week was in his 40s and was returning to the city from the northeastern Ituri province where there had not been any Ebola cases confirmed in the latest outbreak.
It is thought he became exposed to the virus along the 300-mile-long route back to Goma, where he took a number of taxis over a number of days through densely populated areas at the heart of the outbreak.
He arrived in Goma on 13 July and started showing symptoms nine days later.
After that, he was isolated at an Ebola treatment centre having spent five days at home with his family.
The outbreak has been declared as a global health emergency by the WHO – only the fifth in history.
It has meant a surge of millions of dollars in pledges, but health workers warn that a new approach is needed for the region to combat misunderstandings in a part of Congo that had never experienced Ebola before.
There is no official treatment for Ebola, which is spread by close contact with bodily fluids of those infected.