As a new Ebola outbreak rages in Congo, some of the first Ebola virus patients to be successfully treated in the United States during the deadliest recorded outbreak five years ago are reuniting with their doctors on Friday.

Dr. Kent Brantly, Nancy Writebol and Dr. Ian Crozier were three of four Americans who were treated at Atlanta's Emory University Hospital in 2014 and recovered.

Dr. Kent Brantly, the Samaritan's Purse doctor who contracted Ebola while treating patients in Liberia in 2014, was treated and released from Emory University Hospital. David Morrison / Samaritan's Purse

They plan to join Emory medical staff for a media briefing Friday, the fifth anniversary of Brantly's arrival. He was the first to come to Emory after being infected while working in Liberia.

But the celebration of their recovery is being undermined by the latest unrelenting outbreak of the virus in Congo that has killed more than 1,800 people, nearly a third of them children, in the year since it was first detected.

On Thursday, the wife and 1-year-old daughter of the man who died of Ebola in Goma earlier this week tested positive for the disease, health officials said. It marks the first transmission of the virus inside the densely populated crossroads city on the border with Rwanda, a scenario that health experts have long feared as the virus outbreak enters its second year.

Rwanda briefly closed its border with Congo, a city of more than 2 million, as the painstaking work of finding, tracking and vaccinating people who had contact with the man — and the contacts of those contacts — continues.

The man died on Wednesday after spending several days at home with his large family while showing symptoms. Congo's presidency said the entire family was at "high risk" and in quarantine.

But many others are at risk of exposure. The man in his 40s was a miner returning from an area of northeastern Ituri province, the World Health Organization has said. It remains unclear where he was exposed to the virus along the 300-mile journey to Goma and whom else he could have infected while taking motor taxis over a number of days through the densely populated region at the heart of the outbreak.

"We're seeing the first active transmission chain in Goma and expect more to come," the International Rescue Committee's Ebola response director, Andre Heller, warned in a statement.

World Health Organization officials have praised African nations for keeping their borders open to date.

Congo's presidency was quick to condemn Rwanda's decision to prohibit travel on Thursday, and Congolese at the busy frontier expressed frustration.

"I can't understand why they don't just test us instead of closing these borders," said Angel Murhula, who works in Rwanda.

Several hours later, the border had reopened and a Rwanda health ministry statement called the events a "traffic slowdown" as surveillance for Ebola was reinforced. The ministry advised against unnecessary travel to the Goma area.

WHO has recommended against travel restrictions amid the outbreak but says the risk of regional spread is "very high." Any border closure is likely to push people to avoid official crossings equipped with hand-washing stations and where people are checked for signs of fever or other Ebola symptoms. In June, three people who crossed on an unguarded footpath into Uganda died there before their family members were taken back to Congo for treatment.

It is now the second-deadliest Ebola outbreak in history, and last month the World Health Organization declared it a rare global emergency. It has brought a surge of millions of dollars in new pledges by international donors, but some health workers say a new approach is needed to combat misunderstandings in a part of Congo that had never experienced Ebola before.

The 2014-16 outbreak in West Africa remains the deadliest ever recorded, killing more than 11,300 people.