Militants affiliated with the Islamic State set fire to a health center treating Ebola patients in the Democratic Republic of the Congo this week, forcing infected patients to flee amid violence that killed dozens of people, according to health and United Nations officials. At least 44 people were killed in the attacks, officials said. It began Thursday night around Cantine-Aloya, a village about 45 kilometers west of Beni, a city in eastern Congo. Many houses were burned, forcing residents to flee the area. The violence is a serious blow to efforts to contain the Ebola outbreak in the country. Since the first case was detected in May, it has already become the second largest outbreak on record, spreading across a vast area spanning eight provinces in eastern Congo. Infections have declined in some areas, but are rising in places threatened by armed groups that have not been reached by the response effort. After three decades of conflict, more than 100 armed groups are present in eastern Congo. Some of the areas they control or threaten have become Ebola hotspots, hampering urgent efforts to contain the rapidly spreading outbreak. The danger is particularly acute from the Allied Democratic Forces, the group that carried out the attack this week in Cantine-Aloya. Recognized by the Islamic State as an affiliate in 2019, the ADF has a reputation for carrying out especially brutal attacks that often include beheadings, rapes and child abductions. A preliminary report on the attack, based on reports from UN and health officials on the ground, described scenes of terror in Cantine-Aloya on Thursday night and Friday morning. The report, which is not public but was seen by The New York Times, says the attack disrupted efforts to combat Ebola in the area on Friday. Cantine-Aloya has recorded 126 Ebola infections, 83 of them currently under treatment. Among those who fled the city’s health center were a confirmed Ebola patient and five people with suspected cases, three of whom were considered high risk, a local doctor told Reuters. On Friday night, the city’s youth lit bonfires to guard against further attacks, U.N. officials said. The attacks were the latest by the ADF in North Kivu province, one of the most recent hot spots of the Ebola outbreak, after a period of relative calm. UN officials fear that the sudden population movements sparked by the attacks, which led thousands to flee their homes, risk accelerating the spread of the virus. The ADF has around 700 fighters, according to some estimates. But precise information is scarce because the group hides deep in the forests of eastern Congo and has little contact with outside groups. The group has a history of violence against aid workers. In 2013, four Doctors Without Borders employees were kidnapped by ADF fighters in an attack on a village in North Kivu. One escaped a year later, but the other three were never found. The State Department designated the ADF as a foreign terrorist organization in 2021. In recent years it has financed its activities through the gold trade, according to a recent report by the Sentry, a Washington-based research body.