The battle against infectious disease requires organization, resources and a plan. Wars and conflict push the other way: They disrupt basic services, create inaccessible areas and expose aid workers to danger. No wonder disease loves a war zone.

In Syria and Pakistan, this is occurring once again, threatening campaigns against the polio virus, a disease that primarily affects young children. Two years ago, in 2012, the global incidence of polio reached an all-time low and hopes were kindled that we might be on the verge of eradicating the disease.

But polio leapt forward in Pakistan, where it is also endemic, and there were new outbreaks in the Horn of Africa and Syria. In all these locations, a critical challenge is to vaccinate children, and that means health care workers must reach where they live. Unfortunately, war and violence are blocking their way.

In Syria, engulfed in civil war, slow and gradual progress is being made in efforts to vaccinate against polio after an outbreak last year, but there are still tens of thousands of children trapped in conflict zones who are receiving no humanitarian aid at all, much less vaccinations. Both rebels and government forces must realize that polio does not take sides. Much needs to be done, and soon, to deny polio the opportunity to take a larger toll.