Rwanda’s state minister for foreign affairs Olivier Nduhungirehe announced the border closure, which was immediately condemned by the Congolese presidency.
The World Health Organisation has advised against travel restrictions but warns the risk of regional spread is “very high”.
Health experts have long feared an outbreak in Goma, a dense city of more than 2 million people that sits on the border with Rwanda.
A second Ebola death was confirmed on Wednesday after a 40-year-old man spent several days at home with his family while showing symptoms. His 1-year-old daughter has been confirmed as having contracted the virus.
The authorities have begun the arduous task of finding, tracking and vaccinating people who had contact with the man, and the contacts of those contacts.
The man was a miner returning from an area of northeastern Ituri province, Mongwalu, where no cases of Ebola had been recorded, says the World Health Organization (WHO). He was exposed to the virus along the 500-km long route from Komanda to Goma as he took motor taxis over a number of days before arriving home.
He arrived in Goma on 13 July and began showing symptoms by 22 July. He spent the next five days being treated at home when he finally went to a health facility where Ebola was suspected.
1. The new (2nd) #Ebola case at Goma is kind of alarming. Any case would be, but this one has added worrying features. The Ebola response has been working for months to ready Goma for Ebola — to spot it & respond quickly to prevent spread. System didn't seem to work well here.Helen Branswell (@HelenBranswell) July 31, 2019
On Tuesday 30 July, he was placed in isolation at an Ebola treatment centre.
Problem arose leading to the delayed reaction to his symptoms due to confusion with other diseases. Symptoms such as fever are often confused with malaria, which is endemic in the region.
“He many not even have been aware of the exposure that he had,” says Dr Michael Ryan, WHO emergencies chief.
The new death marks one year since the outbreak was declared in Congo. More than 1,800 people have died – nearly a third are children.
The WHO last month declared the outbreak a rare global emergency. It's the fifth time the UN body has raised the alert to this level – a move that has brought with it millions of dollars in aid and new pledges by international donors.
But health workers say a new approach to fighting misconceptions about the virus is fundamental in parts of Congo that have never previously experienced Ebola.
Many people in the region reportedly do not believe the virus is real.
Meanwhile, some health workers responding to the outbreak have been attacked, some killed, in the volatile northeast of DRC where rebel groups are active and the population is suspicious of outsiders.