GENEVA — An outbreak of the deadly Ebola virus in rural Democratic Republic of Congo has spread for the first time to a major city there, the World Health Organization reported on Thursday, raising the threat of a far larger contagion.
The organization said it would convene its emergency committee on Friday to assess the new threat from the disease, which caused one of the most alarming health disasters centered in West Africa a few years ago.
Twenty-three people have died in the outbreak that started in remote rural areas of the Democratic Republic of Congo’s northwestern Équateur Province in early April.
The World Health Organization said the health authorities in the country had confirmed that one person had been infected with the disease in Mbandaka, the provincial capital with a population of more than one million.
“This is a very significant development in the outbreak,” Peter Salama, the agency’s deputy director general and head of its emergency response program.
By Thursday, three people had been confirmed with Ebola virus, including the case in Mbandaka, but 20 other individuals are probably infected and 21 more are suspected cases, including two in Mbandaka. Fifteen people are now in isolation and receiving treatment.
“The challenge will be to stop rapid, explosive expansion of the outbreak in Mbandaka,” Dr. Salama said. “That becomes the number one priority at this point.”
The meeting of the emergency committee, the W.H.O.’s highest level of concern, will review all data and determine whether this Ebola outbreak has become what the agency calls a public health emergency of international concern.
The Ebola outbreak is the Democratic Republic of Congo’s ninth since discovery of the virus in 1976; previous outbreaks were easily contained in remote rural areas.
The arrival of the disease in Mbandaka, a bustling port city, is “a game changer,” Dr. Salama said, adding that “urban ebola is a very different animal to rural ebola.”
Apart from the risks to its own population, Mbandaka’s location on the banks of the Congo River — a highway for the movement of people and goods to the capital, Kinshasa, and a border with the Republic of Congo — escalates the risks of the disease spreading within the country and to neighboring countries.
For the moment, the World Health Organization rates the risk of Ebola’s spreading to neighboring states as moderate and the risk of international transmission as low, Dr. Salama said. Border surveillance is being strengthened in the Republic of Congo and the Central African Republic, and more than a dozen countries in the region have started screening arrivals, he said.
In contrast to the sluggish response to the Ebola epidemic in Guinea, Liberia and Sierra Leone between 2014 and 2016 that claimed more than 11,000 lives, the W.H.O. and international health agencies are rapidly scaling up the expertise and resources to tackle the current outbreak.
Around 60 international health experts have been deployed to Congo, and another 40 are due in a matter of days, Dr. Salama said.
The medical charity Doctors Without Borders has opened treatment centers in the small town of Bikoro, close to the starting point for the outbreak and in Mbandaka. Medical teams have been deployed in the city and the province for the crucial task of tracing and mapping the location of anyone who has been in contact with those known or suspected to be infected. To date they have identified more than 400 contacts, Dr. Salama said.