The term "epidemic" is often used to describe gun crimes in the United States, which got one Yale sociologist curious: just how contagious is it? And how does gun violence spread?
When a disease breaks out, epidemiologists fight back by focusing on transmission. Think needle exchange or sex education programs -- targeted efforts, which try to eliminate contagion pathways -- and combat the spread of disease.
Now, Yale sociologist Andrew Papachristos thinks a similar approach can be taken to the epidemic of gun violence.
"If it's actually an epidemic, it means it should follow certain types of rules," said Papachristos. "It should have certain mechanisms of transmission."
To better understand how gun violence is transmitted, Papachristos and his team examined a network over 130,000 people, publishing the work in the Journal of the American Medical Association. They looked at incidences of "co-arrest" over an eight year period in Chicago.
"Essentially, if you and I commit a crime together," Papachristos said, "robbing a bank, an assault."
The co-arrest data gave Papachristos a kind of social network -- a web of associations between people engaging in risky behavior.
"And then what we do on top of that is we layer out who gets shot and when -- to see how they're related in time and in this social space," Papachristos said. "The result is a social map, essentially, of how these things unfold over time."
"It's akin to this idea of dropping a bit of ink in a glass of water and seeing it spread out and the types of patterns that unfold," he said.
Papachristos said his model could be used with larger demographic data to have a "rapid response" to violence. One that better predicts -- and breaks -- the chains of transmission from one victim of gun violence to the next.
"You could use these sorts of maps to send the right services to the right places at the right time," Papachristos said. "It does need to be a victim-centered approach. If someone is at risk, you need to be able get them the services and warning and help that they need, in a fashion, regardless of any other labels that they might have."