Ebola outbreak suspected death toll rises to 139 as WHO warns of risk of spread

LONDON -- The Ebola outbreak in the eastern Democratic Republic of the Congo had caused 139 suspected deaths with nearly 600 suspected cases as of Wednesday, according to the latest update from World Health Organization Director-General Tedros Adhanom Ghebreyesus.

"We expect those numbers to keep increasing, given the amount of time the virus was circulating before the outbreak was detected," Tedros said during a press briefing in Geneva, Switzerland.

The WHO convened an emergency committee on Tuesday night, following Tedros' declaration of a public health emergency of international concern on Sunday -- one level below a pandemic in the United Nations agency's alert system.

It was the first time a WHO chief had declared such an emergency before convening the emergency committee. After the meeting, the committee agreed that the outbreak did not meet the criteria of a pandemic emergency, which was applied to the global COVID-19 outbreak.

The epidemic was first detected in the DRC's northeastern province of Ituri, with cases officially confirmed by the health ministry on May 15. It marked the 17th outbreak of Ebola virus disease in the DRC, which is Africa's second-largest country and its fourth-most populous nation.

The current outbreak is caused by the Bundibugyo virus, a rare variant of Ebola for which there are no approved vaccines or therapeutics and which requires different diagnostics than other variants. Case fatality rates for previous Bundibugyo outbreaks have ranged from 30% to 50%, according to the WHO.

Tedros said cases of Ebola have been reported in several urban areas of the eastern DRC amid the ongoing outbreak, including the major cities of Goma and Bunia, and that at least two cases and one death have been recorded in neighboring Uganda's capital, Kampala. Cases have also been reported among health workers, according to Tedros.

At least 51 cases have so far been confirmed in the ongoing outbreak.

The WHO chief warned that significant population movement in the region, which includes a high-traffic mining area, along with insecurity and intensified conflict in recent months increase the risk of further spread. The risks are high at the national and regional levels, but remain low globally, according to Tedros.

Among the confirmed cases is an American -- Dr. Peter Stafford -- who was working in the DRC and tested positive for Ebola. Stafford has since been transferred to Germany, Tedros said.

Dr. Scott Myhre, a colleague of Stafford at Serge -- an international Christian missions organization -- told ABC News the doctor was exposed to Ebola during surgery on a "very sick" patient who later died.

Myhre said Stafford developed symptoms that can resemble other diseases including fever, aches, chills and fatigue -- which can make Ebola difficult to diagnose and treat.

Stafford has since received IV fluids and was put on a biocontamination plane Tuesday morning to a U.S. military base in Germany, Scott said. He added that Stafford was put on the plane in a plastic bubble-like contraption to avoid exposing others traveling with him.

Other high-risk contacts, including Stafford's wife and children, are being monitored in quarantine and are expected to be flown to Germany on Wednesday, according to Scott.

Dr. Satish K. Pillai, incident manager for the Centers for Disease Control and Prevention's Ebola response, confirmed at a CDC press conference on Tuesday that six other high-risk contacts "are also having movement plans that are finalizing and will be transiting to Europe as well shortly."

He added that genetic testing from this outbreak shows it is similar to the "genetic fingerprints" from outbreaks in 2007 and 2012, meaning there are diagnostic tools available that can detect this strain of Ebola.

Pillai said on Monday that the agency had activated its Emergency Operations Center through its country offices in the DRC and in Uganda, and is deploying technical experts that have been requested from Atlanta headquarters.

The CDC said Monday that it is preparing to restrict entry for travelers arriving from parts of central Africa where an Ebola outbreak has been declared, in coordination with the Department of Homeland Security.

The risk to the U.S. general public remains low, Pillai said.

ABC News' Youri Benadjaoud, Eric M. Strauss and Mary Kekatos contributed to this report.