A health worker is sprayed with chlorine after visiting the isolation ward at Bikoro hospital in the Democratic Republic of Congo. The hospital had just admitted a suspected Ebola case. Picture: Reuters

NAIROBI, Kenya - Congo has confirmed a case of Ebola in Mbandaka, a city of 1.2 million, marking the first urban case in the latest outbreak of the disease. The World Health Organization's lead response official called Thursday's new confirmed case "a game changer."

Ebola is much harder to contain in urban areas, so this development compounds the risk of contagion and elevates the outbreak to the most serious since an Ebola epidemic that raged across West Africa between 2014 and 2016.

Previously, confirmed cases had been limited to an extremely remote area more than 100 miles south of Mbandaka, in the rain forest of Congo's Équateur province. The case in Mbandaka is only the third confirmed case of the current outbreak; 20 others are probable, and 21 are suspected, bringing the total of potential cases to 44. The death toll is now 23.

"This is a major development in the outbreak," said Peter Salama, the WHO's deputy director general of emergency preparedness and response. "We have urban Ebola, which is a very different animal from rural Ebola. The potential for an explosive increase in cases is now there."

Ebola is notoriously hard to contain, though recent outbreaks in Congo have been managed swiftly by the World Health Organization and Congolese health officials, gaining the government there a reputation as one of the continent's most prepared. Ebola is endemic in Congo, and this is the ninth outbreak of the disease there since the 1970s. Last May, a small outbreak resulted in five confirmed cases and four deaths in a province neighboring Équateur.

The outbreak in West Africa that started in 2014 reached epidemic proportions and was the worst ever recorded, infecting more than 28,000 and killing more than 11,000. 

The disease causes internal bleeding and spreads rapidly through contact with small amounts of bodily fluid. Its early symptoms are not obvious, and the worst effects may take weeks to show. It is often transmitted to humans through the consumption of contaminated meat, but it can also be acquired through any kind of close contact with an infected animal.

The international response to the current Congo outbreak has been substantial and is expected to grow in size and urgency after the announcement of a confirmed urban case. On Wednesday, the WHO delivered 4,000 injections of an experimental vaccine with proven efficacy in recent trials, and more batches are expected soon.

The WHO said it is also deploying 30 "experts" to Mbandaka to "conduct surveillance in the city and is working with the Ministry of Health and partners to engage with communities on prevention and treatment and the reporting of new cases."

The International Federation of the Red Cross and Red Crescent Societies (IFRC) said the first suspected victim was a police officer who died in a health center in the village of Ikoki-Impenge, near Bikoro. After his funeral, 11 family members got sick, and seven died. All seven had attended the funeral or cared for the man while he was sick.

More than 110 Red Cross volunteers in Bikoro and Mbandaka are working to alert surrounding communities and disinfect houses where cases have been suspected. An IFRC spokeswoman said the organization is "kick-starting its response" using stocks of medicine, disinfectant and informational posters left over from last year's outbreak.

A total of 514 people who may have been in contact with infected people have been notified by national health authorities and are being monitored in Mbandaka and Bikoro.

Several tons of supplies are en route to the region, according to a statement from Doctors Without Borders, including "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."

With the confirmed arrival of the outbreak in a major city, the number of people who are likely to have interacted with infected individuals increases exponentially. Mbandaka's dense population and the fact that it is a bustling port both heighten the risk of rapid spread.