When I first saw the musical “Annie,” as a kid, I wasn’t all that interested in the zippy orphan star. I fixated, instead, on President Franklin D. Roosevelt in his bulky wheelchair. Polio put him there, I learned; this was the first I’d ever heard of the virus, from which even White House-bound men weren’t exempt.

I took from that discovery something simple and a little selfish: a child’s sense of relief that Americans had once feared an often-crippling disease until, one day, a page of the script was flipped. In 1952, less than a decade after F.D.R.’s death, a vaccine emerged that reduced the number of U.S. cases from a high of nearly sixty thousand, that same year, to virtually zero, by 1979. After that, polio could be written up as a relic for museums and musicals; we could grow up to be the scourge’s historians, we were told, and not its memoirists.

That “we,” of course, has since proven uncomfortably limited, a symptom of its own “Annie”-style naïveté. Today, polio still claims a certain corner of the globe. A wildly successful eradication campaign reduced new incidents of the virus by more than ninety-nine per cent around the world from 1980 to 2003—a pretty remarkable feat. Yet, just last month, the World Health Organization declared that a revived spread of polio is “a public health emergency of international concern.” All the more striking about this reëmergence is its geography: a map of polio, it turns out, is a map of modern political violence.

Where does polio refuse to die? The three countries where it remains endemic are Pakistan, Afghanistan, and Nigeria. Where else does the risk linger in 2014? The long list of trouble spots includes Syria, Iraq, South Sudan, Somalia, Cameroon, and the Central African Republic, with recent appearances in Gaza and the West Bank.

This month, we’re moving deeper into polio’s “high season,” which, in much of the world, stretches from May until August. If the geography of polio mirrors that of conflict, then the challenge of eradication is, inevitably, as much political and diplomatic as it is epidemiological. And that’s where the plot gets messy.

In recent years, a bright spot of polio-eradication efforts has been Nigeria—a country that also raises some of the most challenging questions about sustaining progress in the absence of peace. The mass abduction of schoolgirls in April made the threat of violence tied to Boko Haram more visible to the rest of the world. It has taken creative tactics by health workers to grow immunization efforts amid the resulting unrest, including efforts by insurgents to thwart them. In February of last year, gunmen on motorbikes reportedly shot dead at least nine female polio-vaccination workers in two Kano-area clinics. The public blame quickly fell on Boko Haram, as well as on certain Muslim leaders who had declared the vaccine a Western conspiracy aimed at causing infertility.

The shootings in Nigeria echoed mass assassinations in Pakistan, where more than sixty polio workers and security personnel have been killed since 2012. Although such attacks have a long history, they were stoked, in part, by reports that the C.I.A. used a phony vaccination campaign in the hope of collecting DNA from Osama bin Laden’s compound in Abbottabad. (After objections from prominent public-health figures, a top White House official announced last month that the C.I.A. had agreed to cease using vaccine programs in spy operations.) Pakistan is now living with the results of anti-vaccine attacks, public distrust, and authorities’ fumbling: at least sixty-six cases have emerged so far this year.

Nigeria, thus far, has largely avoided such a fate. “The insurgents make it very difficult to immunize the children as planned, but that has not deterred us completely,” Pascal Mkanda, who leads the W.H.O.’s efforts on polio in the country, told me recently. He added, “We’ve tried to go around the problem and create innovative solutions.” One example is “firewalling,” whereby vaccinations are given to children entering and exiting the so-called no-go areas that health workers can’t reach. Another involves training local elderly women to create “permanent health teams,” which administer vaccines and other small health interventions quietly, without fuss. There’s also an approach, known as hit and run, whereby immunization teams move quickly into dangerous locations and complete campaigns in a day or two; often, Mkanda says, this means working closely with government security and intelligence forces, getting reconnaissance about “areas where we can go and where we can’t go.”

But such collaborations carry risks, too. Last week, I spoke with the Elisha Renne, of the University of Michigan, an anthropologist who wrote about the relationship between polio transmission and political violence in northern Nigeria for a forthcoming issue of the journal Africa. (She is also the author of “The Politics of Polio in Northern Nigeria,” from 2010.) Renne worries that the government’s perceived rights abuses in their pursuit of Boko Haram—including questionable home raids and the arrests of journalists who air anti-vaccine sentiments—may tarnish the hard-won credibility of health workers who rely on coöperation with police to operate in dangerous areas. “People are afraid of the government; they are afraid of the police,” she said. “Polio workers are seen as part of the government now, in the northeast.” That, too, has its dangers.

The problem of parents refusing vaccines for their kids, it turns out, is far smaller than the problem of children never having the chance to be immunized, owing to political violence thwarting health-worker access. But it’s alarming how quickly that can change. An eruption of anti-vaccine sentiment in Nigeria a decade ago, followed by a wave of infections, made that clear. Oyewale Tomori, who chairs the Expert Review Committee on Polio Eradication in Nigeria, reminded me by phone last week that just two or three cases of polio can quickly escalate to thousands. “In 2010, Kano was dancing … they had overcome the polio problem,” he told me. “Almost immediately, the following year, they almost doubled the number of cases they have, and followed the same pattern in 2012.”

Government support has helped to keep this year’s numbers low, as have community efforts supported by international funders like the Bill & Melinda Gates Foundation, which aids eradication efforts around the world. Still, Tomori fears that, with an election season on the horizon, “the attention of our governors is diverted to getting themselves reëlected.”

“Yes, we’ve made progress,” he said. “But it’s very precious, very tenuous. There are so many factors that can derail us.”

What happens when prevention efforts swerve entirely off the rails? Look no further than Syria. In March, the W.H.O. described the situation there as perhaps “the most challenging outbreak in the history of polio eradication.” Syria was declared polio-free in 1999, a status that it maintained until last year; last October, the country reportedly saw thirteen cases, and the number has only grown since then.

In many ways, Syria’s recent polio outbreak has been the logical result of an obliterated health infrastructure, a decline in public sanitation, weakened access to vaccines, and nearly nine million people displaced from their homes amid the chaos of conflict. In a haunting piece, this past February, for the New York Review of Books, Annie Sparrow reported that six hundred and fifty-two of the country’s nearly two thousand prewar health centers have been destroyed or have closed owing to insecurity or lack of power, largely in opposition-held areas. “This man-made outbreak,” Sparrow writes, “is a consequence of the way that Syrian President Bashar al-Assad has chosen to fight the war—a war crime of truly epidemic proportions.”

A mess like Syria has no genuine borders, as far as infectious diseases are concerned. For the first time in fourteen years, the virus has now spread to Iraq, with whooping cough, measles, and other contagions quite possibly along for the ride.

The “extraordinary event,” as the W.H.O. calls it, of polio gaining ground in 2014 is a global drama in which big victories and heroic efforts can get lost. The villains include not just assassins and thugs but those who have pursued politically expedient interests with insufficient regard for long-term costs. It’s tempting to think of the enterprise of public health as separate from the contingencies of politics and culture, as if those were just distractions. In Thomas Meehan’s novelization of “Annie,” there’s a moment when the President wheels himself over to his Cabinet and pronounces, “The only thing we have to fear is fear itself,” to which his Secretary of the Interior, Harold Ickes, replies, “Ah, baloney.” Sometimes, there is more than fear to fight.

Above: A sub-district supervisor administers an oral polio vaccination to a boy at his home, in the University district of Jalalabad, Afghanistan. Photograph by Anastasia Taylor-Lind/VII.