ARI SHAPIRO, HOST:
Chicago had one of its most violent years in 2016 with a record number of shootings. In a new study, researchers say Chicago's struggle helps prove what some have long argued - that gun violence is not just a law-enforcement problem but a public-health crisis and needs to be treated that way. NPR's Cheryl Corley reports.
CHERYL CORLEY, BYLINE: On the last day of the year in Chicago, there was another grim reminder of how many people lost their lives to gun violence.
UNIDENTIFIED MAN: If you have a loved one who was killed in 2016, you can walk up and down here and find a cross.
CORLEY: Hundreds of people picked up wooden crosses and marched down Chicago's Michigan Avenue to pay tribute to the 762 people killed by guns. Fulicia Suarau, with family members, carried a cross and photos of her grandson, 17-year-old Elijah Jones, who was killed December 6.
FULICIA SUARAU: Something has to be done. It has to stop. It has to stop. We can't do another year like this.
CORLEY: There were more than 4,000 shootings, not all of them fatal, in the city in 2016. Yale University sociologist Andrew Papachristos has studied the city's violence for years and says the number of shootings in Chicago showed that gun violence nationwide is a public-health epidemic. In a study released today in The Journal of the American Medical Association, Papachristos and others explain and predict gun violence in Chicago through what they call social contagion.
ANDREW PAPACHRISTOS: So if I get shot, for instance, there's a high likelihood that the people around me in my networks will also be victims and that, then, their friends will be victims. And their friends' friends will be victims.
CORLEY: The research is an analysis of the social network of individuals who were arrested together for the same offense over an eight-year period. They were trying to understand the patterns of gun violence by literally looking at it like a public health epidemic like AIDS and tracking how shootings spread among a group of about 130,000 individuals.
PAPACHRISTOS: Not only is it an epidemic. We can actually show in our study how it's transmitted and actually specific individuals who may be at risk. And so when you look at the network figures in the study, every one of those little dots is a real human being.
CORLEY: Papachristos thinks this type of contagion study could provide an almost real-time response to shooting outbreaks by analyzing the patterns of shootings, the individuals at risk and sending out people who could intervene - not just the police. Chicago Police Superintendent Eddie Johnson agrees. He supports working with other groups even though the city does plan to hire hundreds more police officers in an effort to fight the gun violence here.
EDDIE JOHNSON: The police department is only as strong as the faith that the community has in it. And I believe that because if the community believes in what we do, and they're a partner in what we do, and we're a partner in what they do, then that will help reduce a lot of this gun violence we see.
CORLEY: Gary Slutkin heads Cure Violence, a violence-prevention model used in more than 50 cities but mostly dropped in Chicago because of funding. He says gun-violence resources typically go to law enforcement. But as this latest study shows, that's only part of the puzzle.
GARY SLUTKIN: This takes us out of morality. This takes us out of - these are good people and bad people - into - there's something going on. It is contagious and that, when it's managed as a health issue, you can rapidly drop it and sustain drops for long periods of time.
CORLEY: Slutkin says that's proven to be true in other big cities like LA and New York, which fund violence-prevention programs and have levels of gun violence far below those in Chicago. Cheryl Corley, NPR News, Chicago. Transcript provided by NPR, Copyright NPR.