It’s that time of year again. With summer’s arrival, people flow into the streets of America’s poorest urban neighborhoods. Temperatures rise and tempers get shorter. Old beefs between corner drug crews start to simmer again as warm weather brings more addicts to the neighborhood, sparking territorial disputes over the swelling black market. Violence can come to the city in many ways, but it comes, like clockwork, when the weather warms up.

In the past month alone, Philadelphia has seen an 86 percent spike in homicides, bringing the year’s tally to 173. Nearly thirty people were shot in the city over Memorial Day weekend alone. In Chicago, a rash of summer gang violence has the city in a state of emergency, as its homicide total soars 50 percent over last year’s. Some in the press have labeled it “worse than Afghanistan.”

Until the sudden eruption of gun violence in Chicago, 2012 had been a good year for Dr. Gary Slutkin. In 1995 he founded CeaseFire, the Chicago-based public health program committed to curbing gun violence in the city’s most afflicted neighborhoods. In the past few years, the infectious disease expert turned urban interventionist had been seeing the fruit of his labors. A 2008 research evaluation of CeaseFire showed that the program reduced shootings in the city’s most dangerous neighborhoods by as much as 40 percent and even completely eradicated gang-related retaliation homicides in some parts of town. This February, The Interrupters, an award-winning documentary about CeaseFire, aired to mass acclaim on PBS’ Frontline. Ameena Matthews, CeaseFire outreach worker and the movie’s charismatic star, did a slew of high-profile interviews for an admiring press about her frequently dangerous work. Stephen Colbert called Matthews an “antibody” against urban violence.

But even more important than awards and accolades was the publication of a study out of Johns Hopkins in January, showing that a CeaseFire-based model in Baltimore—Safe Streets Baltimore—had worked, achieving similarly dramatic reductions in gun violence as in Chicago over a three-year period, between 2007 and 2010. Ceasefire’s Baltimore program reduced homicides in Cherry Hill, one of the city’s most violent neighborhoods, by 54 percent; non-fatal shootings dropped by 34 percent. Indeed, mounting evidence suggests that CeaseFire, which has grown from a handful of employees to a nationally recognized brand name, looks to be the real deal: a game changer when it comes to the intractable problem of violent crimes in urban centers. Efforts are now under way to scale the program up, exporting it around the globe.

“We’re in Baltimore, New York City, Philadelphia, New Orleans, Kansas City,” says Slutkin, speaking from his office in Chicago and projecting total confidence in his program’s ability to change not just urban America but the world. “We’re in other countries: Trinidad, South Africa, Kenya, Iraq—and the list is growing.

Some researchers have regarded CeaseFire with doubt. Dr. Daniel Webster, associate director of Johns Hopkins’ Center for the Prevention of Youth Violence and lead author of the study of Safe Streets Baltimore, admits he was a Ceasefire skeptic—until he parsed the data.

“The magnitude of the positive results to me was quite impressive,” Webster says. Controlling for concurrent law enforcement efforts and other factors that could skew results, one neighborhood saw a 56 percent drop in murders after the Safe Streets program began. Another saw a 53 percent drop. “I assumed that it would take a long time to see improvements, but the reductions happened rather abruptly,” Websters says. “It suggests to me that there’s pent-up demand for this type of intervention.”

Yet, with gang violence raging across Chicago this summer as if Ceasefire had never existed, the question arises: What happened, and does it bring doubt onto Slutkin’s methodology?

* * *

“Violence is a Disease,” the CeaseFire homepage proclaims. This concept is the basis for the program, which Slutkin founded based on his theory that violence is a learned pattern of disordered behavior. When violence breaks out, the theory goes, it is possible to prevent it from spreading among peers by blocking transmission like an infectious disease. Having worked with the World Health Organization on the Ugandan AIDS epidemic, as well as spending years in Africa and San Francisco fighting tuberculosis outbreaks, Slutkin knew how to build models for fighting infectious diseases. He designed a violence-prevention model along the same lines.

Is violence really an infectious disease? It turns out that it behaves sufficiently like one for the same principles to apply in combating it.

CeaseFire works through aggressive peer-led street outreach by ex-offenders with deep ties to the community, who gather intelligence on gangs in order to spot potential conflicts. Such conflicts are then mediated by the program’s famed violence “Interrupters.” At its peak, CeaseFire Chicago employed fifty outreach workers and fifty Interrupters, chosen from pools of candidates screened by professional and community panels to ensure they’d left the hustling life. Statisticians analyze the data gathered by outreach teams alongside data tracking violence collected by law enforcement, identifying up-to-the-moment crime hot spots, and focusing the program’s resources on those places where recent flare-ups of violence have potential to multiply through retaliation, breaking out and infecting whole neighborhoods.

Unlike harsh police crackdowns that can create an adversarial relationship with the community, CeaseFire’s first task is to establish its credibility as an ally in the fight against violent crime. It does this by relentlessly canvassing a given neighborhood, building relationships with corner drug dealers and truant youths, as well as the families, local leaders and faith groups who support its work. Outreach team members visit hospitals to counsel gunshot victims and go to funerals to stand alongside the friends of murdered street associates. They get access cops can’t get; kids involved with guns and drugs will talk openly and honestly with CeaseFire workers because of their shared history of hustling dope and packing straps. Not seen as snitches, CeaseFire outreach workers can get privileged details about grudges between gangs that could flare into open war. In addition to preventing this kind of violence, CeaseFire workers continue to engage with the youths involved to change the cultural norms that make retaliatory shootings seem like rational responses to perceived slights and petty disses.

The Interrupters captures how risky this kind of intensive field work can be; weapons sometimes come out while CeaseFire is on the scene and outreach workers have even taken bullets for the program. But the film also shows how the intensive mentoring provided by CeaseFire teaches young men and women to find constructive ways to resolve conflicts rather than reaching for a gun. The results are astonishing; over the course of three years CeaseFire entirely eradicated retaliatory homicides in four Chicago neighborhoods and nearly halved them in three others. Such results stand in sharp contrast to law enforcement crackdowns that can actually spread violence into previously uninfected communities, as gun-strapped hustlers “fall back,” fleeing cop-targeted hot spots and moving to less violent neighborhoods where they aren’t immediately recognized by police.

“We’re like the iPod in a world of tapes or vinyl records,” Slutkin says, referring to cities stuck on older, law enforcement–driven approaches to violence. “But whereas consumers get to choose an iPod, neighborhoods don’t get to choose whether they want enforcement and punishment or epidemic control and behavior change. Usually they still just get crackdowns, arrests and imprisonments.”

Slutkin sees Chicago’s recent uptick in violence as symptomatic of how much the city has come to rely on his program. Indeed, a similar phenomenon occurred in 2008, when a temporary pause in CeaseFire’s efforts was accompanied by a spike in violence. He notes that infectious diseases like tuberculosis and measles similarly return when public health efforts to control them are abandoned.

“This is a wave on top of a wave [of violence] that began last fall when Ceasefire temporarily dropped off from ninety-nine to fifty-three outreach workers,” he says, noting, “CeaseFire has added outreach workers in response.” He also points to the fact that CeaseFire workers only cover a third of the city—and in those areas there have not been spikes in violence.

* * *

Philadelphia’s own rise in summer violence was precipitated by a freak mid-winter spike in murders that left thirty-four dead in January, just as its fledgling CeaseFire program was emerging from the pilot phase. Philadelphia is ranked sixth in homicides nationwide among cities with a population greater than 500,000, and five months later its violence trend hasn’t snapped; there were 173 murders as of mid-June, compared to 140 this same time in 2011.

Looking at Philadelphia CeaseFire, it’s hard not to feel like Slutkin’s rhetoric about Ipods and vinyl records and global game changers is getting ahead of itself. Strictly grassroots and thinly funded, the program comprises a street outreach team (and paid staff) of only four people, led by Executive Director Marla Davis Bellamy. Working out of a small office space on Temple University’s campus, the program uses volunteer undergraduate criminal justice majors for extra manpower to help locate social services for its clients.

An attorney with experience in public health, Davis Bellamy holds dual appointment at Temple University’s law and medical schools and has an advanced degree in government administration from the University of Pennsylvania. Her outreach team brings the typical mix of CeaseFire street wisdom and deep neighborhood intelligence to the table. More than that, team members are hungry for results, relentlessly canvassing the neighborhoods where they work, while Davis Bellamy pushes hard to make political inroads with the city’s top brass.

The program was piloted in the North Central Philadelphia’s 22nd Police District, a desperately poor and persistently violent stretch of land, pocked with crack cocaine corners and dense with urban blight. Davis Bellamy is quick to point out that, of the rash of murders back in January, “only one of those was in the area we’ve been working in.” Like Slutkin’s conclusion about Chicago’s recent violence, Davis Bellamy believes there are similar indications that the program is already making a difference, with Philadelphia’s most violent police district appearing to have largely bucked the recent trend.

But Philly’s violence hot spots remain numerous, spread across a vast territory encompassing multiple neighborhoods and ethnic groups. How do a team of four and a single director get their arms around this?

“By being persistent, man,” says Terry Starks, tall and stocky in a bright orange CeaseFire outreach worker sweatshirt that matches his henna-dyed Muslim’s beard. “People in the neighborhood have been disappointed before [by social programs]. At the scene of a shooting they’ll ask us, ‘Is this the only time I’m gonna see your face?’ That’s why we’re out there every day, we call our clients every day, we’re constantly checking on them.”

Starks, a onetime gunshot victim who spent much of the last fifteen years bouncing in and out of jail on a host of drug and other charges, including attempted murder (ultimately withdrawn), agrees with Dr. Webster’s assertion that there’s a pent-up demand for this type of intervention. In Philly, he says, the CeaseFire team is welcomed in places where cops are not and has easily made connections, despite a pervasive Stop Snitching street code in North Philly—long derided by police and politicians as a cancer on the city—where sharing any information about a person’s drug operations or criminal involvement is nearly certain to result in violent retaliation. Witness intimidation has plagued city courts, hindering the District Attorney’s ability to get convictions against violent criminals. Threats against those who would cooperate with authorities are scrawled in graffiti all over the city’s hottest drug corners.

This makes the trust forged by CeaseFire workers critically important. “When we roll up on the corner, dudes are like, ‘What’s up oldhead?’ ” says Starks. “Because they know who we are, they want to check out what we’re doing, they’ll take our pamphlets and hear our message.” He points to a time a young man refused to take a pamphlet “because there were people on the corner watching us talk.” But as they left, Starks turned around to see the man cautiously take the literature from another corner kid. “People want to learn about this.”

The youngest of CeaseFire’s Philly four outreach workers is 23-year-old Nortavin Rogers, who goes by his street name, “Black,” even around the office. While CeaseFire’s Chicago work has been largely facilitated by the predictable patterns of retaliation that occur between known gang affiliates, Black points out that Philly’s violence problems aren’t driven by gangs. “Some dudes try to bring that [gang] stuff over from Jersey, but they find out real quick that ain’t nobody in Philly give a shit what color you wearing,” he says. Instead, violence is driven by fractious networks of ragtag corner drug crews and pill-popping, PCP-smoking stick-up cliques.

“In Philadelphia [violence] is a moving target because of these cliques or crews that split, regroup and split again,” says Dr. Slutkin. “But this [fragmentation of gang culture] is the new normal, it’s happening in many cities.” Figuring out how to adapt is one of the challenges CeaseFire faces. “Cities also will differ in characteristics of violence; the distribution, forms, structures,” he continues. “…. It just means that calculating [through street-level data collection] how to deploy our workers is critical.”

From city to city, another hurdle to overcome is politics. Many mayors and local politicians pay lip service to the need for innovative, evidence-based social programs, but when it comes to funding, implementation and long-term investment, political calculations can trump programs that actually work. Particularly in an atmosphere of severe austerity—Republican Governor Tom Corbett is working to eliminate welfare funds for single adult recipients, a safety net program for the poorest in the state that has existed since the New Deal—public funding for social programming is seen as a fiercely competitive zero sum game. Nobody wants their piece of the pie jeopardized to pay for new programs run by unfamiliar players, no matter how promising. And in at least one city (which Slutkin did not wish to name), rather than pay to import replication efforts, officials have tried to create knock-off CeaseFire programs by reworking pre-existing (and ineffectual) violence prevention programs run by insiders.

Slutkin stresses science over politics. “CeaseFire is a very specific and replicable system,” he says. “Like a vaccination campaign, you need the right ingredients, the right dose, given at the right time by trained professionals. Many agencies may say, ‘We’re already doing that,’ or, ‘We can do it ourselves,’ but they soon learn that there is more to it—and are grateful for the new training.”

There is a palpable sense of anxiety at Philadelphia CeaseFire over funding. The program is paid for only through June 30, at which point it could conceivably fold without an infusion of cash. Recently, Davis Bellamy says, they’ve been trying to tap into federal funds, and are preparing a grant that would fund a new operation in the city’s 25th police district—a notorious neighborhood and the nexus of Philly’s heroin trade—should their efforts in the 22nd District wind down.

Both Slutkin and Davis Bellamy say they have met with Mayor Michael Nutter and feel like he’s behind them. And contrary to the kinds of tensions one might expect between police and ex-offenders working at the same crime scenes, the police department welcomes any help it can get in wrestling down the murder numbers. Davis Bellamy stresses that Philadelphia Police Commissioner Charles Ramsey has been a strong ally, as has Captain Branville Bard of the 22nd District. Still when asked by The Nation about providing the funding necessary to make CeaseFire a permanent addition to Philadelphia’s roster of public health programming, and expanding it into more gun violence–plagued neighborhoods, Mayor Nutter’s office declined to respond.

Part of Slutkin’s intent in medicalizing violence was to shield CeaseFire from funding pressures by making prevention part of every city’s budget. If violence is a behavioral disorder that spreads like an epidemic rather than a criminal act rooted in immorality, his argument goes, then there should be a dedicated funding stream to control outbreaks, as is done with tuberculosis, and treat it the way we do other behavioral health disorders like drug addiction.

Even with the funding odds against them, the Philly team is clearly ready to do more than survive. Confronted with the possibility that they could soon lose their paychecks, Davis Bellamy pep-talks her outreach staff. “Remember guys,” she tells them, “the Chicago program started with four people too.”