An Ebola outbreak in the Democratic Republic of the Congo has spread to a large city and the World Health Organization has called an emergency meeting to talk about what to do.

A case of Ebola in a city is a serious matter. Ebola regularly breaks out in remote, rural parts of Africa but usually causes only a few dozen or a few hundred cases. In 2014, when it hit a more connected region of West Africa with several urban centers, it spread to more than 28,000 people and killed 11,000 of them.

“The challenge just got much much tougher," said Dr. Peter Salama, who heads WHO's emergency program.

A case in a city is "a game changer," he said.

WHO has called an emergency meeting to decide whether to raise the threat alert level.

WHO says 44 cases of Ebola have been reported in the Democratic Republic of the Congo — most in a remote, northwestern province that is very hard to reach. More than 20 people have died.

The new case is in Mbandaka, a city of nearly 1.2 million people on a major river.

“This is the ninth Ebola outbreak in Congo in the last 40 years,” said Henry Gray, emergency coordinator for Medecins Sans Frontieres (MSF or Doctors Without Borders) in Mbandaka.

“So far, all of them have occurred in remote and isolated areas, as was the case last year in Likati, when the epidemic didn’t spread. With the new case confirmed in Mbandaka, the scenario has changed, and it has become more serious and worrying, since the disease is now affecting an urban area," added Gray, whose group is helping lead efforts to stop the outbreak.

"It is paramount to trace the suspect case in order to have a clearer view on how it reached the city."

More than 500 people are being monitored. With Ebola monitoring, people check for fever daily and report any symptoms to health authorities.

"This is a concerning development, but we now have better tools than ever before to combat Ebola," said WHO Director-General Dr. Tedros Adhanom Ghebreyesus. “WHO and our partners are taking decisive action to stop further spread of the virus."

WHO has admitted to moving far too slowly and timidly to help fight the 2014 epidemic of Ebola in West Africa.

Confirmation of urban #Ebola in #DRC is a game changer in this outbreak - the challenge just got much much tougher https://t.co/UFA3zBh4by @WHOAFRO — Peter Salama (@PeteSalama) May 17, 2018

The first batch of 4,000 vaccines has arrived in the DRC’s capital. The vaccine is still experimental, but appears to have protected people from Ebola when it was tested in Guinea in 2016. Drugmaker Merck has licensed the vaccine, which was developed in Canada, and has been seeking U.S. Food and Drug Administration approval.

Researchers who tested the vaccine used the same strategy that was used to eradicate smallpox in the 1970s. Called ring vaccination, it calls for vaccinating people who have been in contact with patients, and contacts of contacts.

#Ebola vaccines arrived in Kinshasa today, ahead of deployment to affected health zones in #DRC. pic.twitter.com/5rSkle9K8g — Peter Salama (@PeteSalama) May 16, 2018

But the vaccine must be kept in especially cold conditions — far below the level of normal freezers — which makes transporting it in such a remote region a challenge.

The U.S. Centers for Disease Control and Prevention is working with other groups to help.

"We have about a dozen staff (laboratory diagnostics, epidemiologists, healthcare worker safety, data management, emergency operations) ready to deploy when WHO gives the green light," CDC spokesman Tom Skinner said.

"In the next few days, several tons of supplies will arrive in Mbandaka—including medical kits; protection and disinfection kits containing isolation items such as protective clothing, gloves, and boots; logistical and hygiene kits containing items such as plastic sheets, chlorine spray kits, and water treatment kits; and palliative drugs to treat Ebola symptoms, such as strong painkillers, anti-anxiety drugs, and antibiotics," MSF said.

"Among the MSF staff on the ground are some of our most experienced Ebola responders, including medical personnel, experts in infection control, and logisticians."

Ebola causes a hemorrhagic fever — one that can cause internal and external bleeding. It also causes a high fever, vomiting and diarrhea. The virus spreads through close contact with blood and bodily fluids.

Common burial practices, which include washing the bodies of the dead, can help the virus spread.