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 devastated West Africa a few years ago.
Twenty-three people have died in the current outbreak, which started in remote rural areas of the Democratic Republic of Congo’s northwestern Equateur Province in early April.
The World Health Organization said the health authorities in the country had confirmed that one person was infected with the disease in Mbandaka, the provincial capital, which has a population of more than one million.
“This is a very significant development in the outbreak,” said Peter Salama, the agency’s deputy director general and head of its emergency response program.
By Thursday, three people had been confirmed to have the 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 No. 1 priority at this point.”
The meeting of the World Health Organization emergency committee will review all the data and determine whether this outbreak has become what the agency calls a public health emergency of international concern.
The outbreak is the Democratic Republic of Congo’s ninth since the 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.”
The arrival of Ebola in Mbandaka poses a risk beyond the city’s own population. Mbandaka sits on the Congo River, a highway for the movement of people and goods to the capital, Kinshasa, and a border with the Republic of Congo.
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 of 2014 to 2016, which claimed more than 11,000 lives, 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 of 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 of being infected. To date they have identified more than 400 contacts, Dr. Salama said.
That operation provides the basis for a vaccination campaign targeting front-line responders and those exposed to the disease. The goal is to encircle the outbreak. The World Health Organization shipped 4,000 doses of a newly developed Ebola vaccine to Kinshasa on Wednesday, and vaccination could start on Monday, Dr. Salama said.
The vaccine will be kept in the capital until shortly before use because of the lack of facilities in the provinces for storing it at the required temperature, between minus 60 and minus 80 Celsius.
Such difficulties underscore the severe logistical challenges to fighting the disease in remote and rugged terrain with few roads, little electricity or basic services, and no facilities for health workers to live and work in.
International agencies are sending in protective equipment for health workers, body bags to enable safe burials, chlorine-spraying equipment, water treatment kits and medicines.
But the infection area has no airports that can handle large planes. Mbandaka is accessible only by small aircraft and Bikoro only by helicopter. Villages beyond Bikoro where the outbreak is believed to have started have so far been reached only by motorbike.
In one hopeful sign, Dr. Salama said, the two suspected cases in Mbandaka involve brothers believed to have contracted the virus at a funeral ceremony in Bikoro.
So health officials say the infection was probably part of the same transmission chain as the earlier cases in the outbreak, and not evidence of a different chain that had been developing undetected. That would pose a far more complex challenge in controlling the outbreak.