The World Health Organization on Wednesday declared the Ebola outbreak in the Democratic Republic of the Congo a "public health emergency of international concern," a rare designation only used for the gravest epidemics.

The 1-year-old Ebola epidemic in eastern DR Congo, the second deadliest on record, has largely been contained to remote areas, but this week saw a patient diagnosed with the virus in provincial capital Goma, the first case in a major urban hub. "It is time for the world to take notice," WHO chief Tedros Adhanom Ghebreyesus said, as he accepted the advice of his advisory board to invoke the emergency provision, activated by the UN health agency only four times previously. 

Those included the H1N1, or swine flu, pandemic of 2009, the spread of poliovirus in 2014, the Ebola epidemic that devastated parts of West Africa from 2014 to 2016 and the surge of the Zika virus in 2016.

The Ebola virus is highly contagious and has an average fatality rate of around 50 percent. It is transmitted to humans from wild animals and spreads among people through close contact with the blood, body fluids, secretions or organs of an infected person.

Responders had hoped that this Ebola outbreak would be easier to control, thanks in part to a new vaccine.

While more than 160,000 people in the affected provinces of North Kivu and Ituri have been vaccinated, containment efforts have been hampered by chronic unrest in the region and a lack of trust in communities for health workers. 

A panel of top WHO officials that met in Geneva on Wednesday to issue the emergency call expressed "disappointment about delays in funding which have constrained the response."

A fresh UN funding appeal for $700 million to cover the ensuing six months is expected in the coming days. 

Reacting to the emergency declaration, the president of Doctors Without Borders, Joanne Liu, called for "a change of gear" in the response to the outbreak.

"We need to take stock of what is working and what is not working," she said.  

The International Federation of Red Cross and Red Crescent Societies welcomed the decision, voicing hope that the emergency call "will bring the international attention that this crisis deserves."

Since August last year, the DRC Ebola outbreak has killed more than 1,600 people out of more than 2,500 cases.  

WHO has held off on making the emergency declaration on three previous occasions, but the confirmation of a case in North Kivu's capital Goma escalated the crisis. 

Tedros this week called the Goma patient a "potential game-changer," because the city is a "gateway" to Africa's Great Lakes region and the wider world.

The Goma patient has been described as an evangelical preacher who traveled to Goma from Butembo, one of the towns hardest hit by Ebola.