Is gang violence infectious? MSU study suggests yes.

Aug 31, 2015

A new study out of MSU adds credence to the idea that some kinds of violence are actually predictable in the way they spread through a community. Associate Professor of criminal justice April Zeoli talks about her research tracking gang violence as an infectious disease. 

April Zeoli is an Associate Professor at Michigan State University's School of Criminal Justice.
Credit Michigan State University

To most of us, violence can seem random. But what if we could actually predict the way violence spreads? A new study from Michigan State University's School of Criminal Justice suggests we can. 

Epidemiologist named Gary Slutkin first put forth the idea that some kinds of violence spread much the way an infection does. He founded a group in Chicago called CeaseFire, that worked at interrupting the spread of violence.  Now, a new ground-breaking study out of MSU actually gives hard data to support that idea. Current State's Melissa Benmark talks to April Zeoli, an Associate Professor in MSU’s School of Criminal Justice and lead author of the report, about her research. 


What did the study find? 
We found that there were two types of homicide that didn't “cluster” or didn't have hotspots and those were robbery homicide and intimate partner homicide. Those types of homicide seem to be randomly placed in space and time throughout the city of Newark, which is where we did the research. The other types of homicide all clustered, so there were little hot spots of these types of homicides. 

But only one type of homicide showed a pattern of the new movement throughout the city of Newark through time, and that was gang-motivated homicide. What was particularly interesting was that in areas where gang homicides were prevalent, we also saw hotspots of revenge homicides and drug-related homicide. So it looks like there's a common cause or facilitating factor that leads to many types of homicides and erupting in those areas at those times.

Which also I suppose kind of fits the infectious disease metaphor. So these killings make the area more susceptible to other kinds of killings? 

Yes, or the infectious agent is spawning all of these types of killings. So there's a facilitating factor or a common cause. 

A facilitating factor might be the prevalence of guns in the area. If many people are carrying guns, disputes can turn lethal fairly quickly. You know it could've also been the influence of the gangs. As I mentioned, gang members committed a lot of these other homicides as well. So if gangs were becoming more violent that could've spilled out into other types of homicides. 

How does it spread?

There are three things that and infectious disease need to spread. The first thing is the source of the infection. For homicide this is conditions that make it likely that interactions will lead to homicide. And I already mentioned that the presence of firearms makes it more likely that a homicide will occur. Gang activity, which is what we think happened here, will make homicide more likely. The presence of drug markets, so a lot of the illegal drug activity can make a homicide more likely. 

The second thing a disease needs to spread is a way to spread. For homicide this can be person to person, word of mouth. So if someone finds out that a member of their gang was killed by a member of another gang, they may take revenge, they may retaliate and commit homicide. But it can also spread through fear of homicide. As an area becomes more dangerous, people may take steps to protect themselves and that can include arming up, carrying more weapons, being less willing to seem weak. 

And the third thing a disease needs to spread is a susceptible population. Research has shown that those who live in economically disadvantaged areas, particularly the young minority male, seem to be the most susceptible to homicide.