There have been 131 suspected deaths and 500 cases of the Ebola strain in DR Congo, according to the WHO.
"Early on Sunday, I declared a public health emergency of international concern over an epidemic of Ebola disease in the Democratic Republic of the Congo and Uganda," Tedros Adhanom Ghebreyesus told the World Health Assembly in Geneva.
"I did not do this lightly... I'm deeply concerned about the scale and speed of the epidemic," he said.
A WHO official has warned that the outbreak of Ebola could be lengthy, with the WHO and Africa Centres for Disease Control and Prevention declaring it as a public health emergency.
The Bundibugyo strain has a 40% fatality rate and does not have a vaccine or treatment to fight it.
Dr Mosoka Fallah, acting director of the science department at Africa CDC said that "When you have an outbreak with a strain that does not have countermeasures, we are going to advise on the best approach to take."
"We will look at what evidence we have and make a decision," he continued.
Last night the Africa Centres for Disease Control and Prevention declared the outbreak as a Continental Public Health Emergency.
"Africa CDC expresses deep concern about the high risk of regional spread due to intense cross-border population movements, mobility related to mining activities, insecurity in affected areas, weak infection prevention and control measures... and the proximity of affected areas to Rwanda and South Sudan," it said.
Africa CDC head Jean Kaseya said: "This outbreak is occurring in one of the continent's most complex operational environments, marked by insecurity, population mobility, fragile health systems, and the limited availability of medical countermeasures for Bundibugyo strain Ebola virus disease."
According to Sky news, a WHO official in eastern Congo has discussed the possibility of a vaccine for the Bundibugyo Ebola strain, she revealed that a group of experts were to meet with the WHO today to discuss vaccine options.
A doctor from the US has tested positive for Ebola after being exposed while working with a medical missionary group in the Democratic Republic of Congo, US officials say.
The German health ministry has said that they are preparing to host and treat the infected US citizen. "US authorities have requested assistance from the German government in treating a US citizen who contracted Ebola in Congo," a German health ministry spokesperson said.
"Preparations are currently under way to admit and treat the patient in Germany," the spokesperson said, however no other details were given.
