A police officer shelters behind a hospital sign as police guard a hospital in Butembo, Congo, on Saturday after militia members attacked an Ebola treatment center in the city’s Katwa district overnight. (Al-Hadji Kudra Maliro/AP)

WHEN THE Ebola virus appeared in Congo last year, the 10th outbreak in four decades, there was some hope of progress against what very often produces a trail of death. The hope was that a new vaccine developed by Merck after the epidemic in 2014-2016 would be effective and contain the outbreak, if enough people could be inoculated. Many months later, the news about the Merck vaccine VSV-EBOV in a clinical trial is promising indeed: It has shown to have an almost 98 percent efficacy.

But lately, worrisome developments have overtaken the good news. Ebola infections are rising. The reasons offer a window on the dangers when war and insecurity mix with disease. Human fears and ignorance aggravated by military coercion and violence create formidable medical and biological challenges. This same lethal nexus is showing itself in the cholera epidemic in war-ravaged Yemen, and in the attacks on anti-polio campaigners in Afghanistan and Pakistan. Global public-health authorities need to figure out not only how to save lives with medical treatment but also how to do so in war zones, as is sometimes accomplished, albeit with difficulty, in humanitarian relief.

In the case of Ebola, the primary health-care tactic is to contain the virus inside a ring, interrupting transmission, a process that requires several steps: surveillance, case investigation, contact tracing and vaccination. In the 2015 West Africa outbreak, which killed more than 11,000 people, that proved extremely difficult. The success of the new vaccine, with more than 100,000 inoculated so far, has given health-care workers and others an important tool to interrupt transmission in the provinces of North Kivu and Ituri. So far, Ebola is largely confined to that one area of Congo and has not spread as widely as the West Africa epidemic. As of April 22, there were 1,353 confirmed and probable cases, with 880 deaths.

Yet, lately, case counts have risen to double digits on many days. A surge of violence has intimidated many people from seeking treatment, making the virus harder to contain. The region is a battleground for an estimated 120 militias, a conflict fueled by the presence of valuable minerals. In February, a Doctors Without Borders treatment facility was partially burned down. The State Department has ruled the area off limits for security reasons, so the Centers for Disease Control and Prevention is not on the ground, but many public-health and medical responders from Congo and elsewhere, including nongovernmental organizations and the World Health Organization, are bravely at the front lines and struggling. A WHO epidemiologist was killed in an attack April 19. The WHO response has been far better than its disastrous performance in 2014 but is still $104 million short of what’s needed to fight the outbreak. Everyone needs to wake up to the urgent needs and long-term lessons, before Ebola again jumps the fence.