TO UNDERSTAND why the Ebola virus disease is spreading in Congo, think of a fire. The virus burns in a fire pit and periodically leaps out. Health workers scramble to contain the outbreaks, which sometimes strike in locations by surprise. Thus, it is alarming to hear from the World Health Organization that responders are being forced to retreat on some days because of the dangerous security situation created by armed militias .

So far, Ebola has not leapt over international boundaries, and teams of extremely brave health-care and medical workers are trying to execute the tactic that has worked before: contain the virus inside a ring, interrupting transmission. This requires a skillful choreography: surveillance, case investigation, contact tracing and vaccination. Unlike the 2014-2016 West Africa epidemic that killed more than 11,000 people, today’s responders have a vital tool in an efficacious vaccine.

But now the WHO has announced that the public-health and medical responders are, in some cases, being forced to suspend work because of the militia attacks. The outbreak is located in two provinces in eastern Congo: North Kivu and Ituri. In two of seven hot spots, Butembo and Katwa, both in North Kivu, the workers have been “reduced to a ‘stop and go’ pattern, where a day or two of activity is followed by a day or two of suspended or limited activity,” the agency said. Imagine a fire in which the firefighters have to retreat for a few days.

Another serious concern is that 40 percent of the deaths are occurring outside treatment centers. This means people are dying in their communities, where the highly infectious virus is easily transmitted to others, and detection delayed. A report in The Post says the problem of mistrust of doctors in the community, as well as danger to them of violent attack, has led some medical personnel to essentially go undercover to carry out their lifesaving efforts.

The outbreak has killed 1,073 people out of 1,672 confirmed cases since last summer, the second-worst Ebola outbreak on record. Armed with the vaccine, the WHO has shifted its strategy, lowering the dosage and widening the eligibility to reach more people. But as Australian virologist Ian Mackay points out on his blog, “a revised vaccine strategy . . . can’t succeed unless security is improved, people feel that it’s improved, and community trust is achieved. A vaccine that people don’t want or can’t get, won’t work.”

Improving security is not a simple matter. Bringing armed forces into the region might further complicate the trust problem in communities. In the West Africa epidemic, authorities realized belatedly that forced quarantines created panic and were counterproductive. Trust cannot be coerced but must be won. New approaches are desperately needed. The armed militias are, by their actions, allowing the Ebola virus to spread. As Mr. Mackay has pointed out, the time it takes for every 200 newly confirmed cases or deaths is growing shorter and shorter. The fire is burning.

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