The Homicide Virus

By Joshua Brooks

Before epidemiologist Dr. Gary Slutkin’s Ceasefire Chicago program Martin Torres might have gotten off the Greyhound bus he rode to Chicago for his favorite nephew Emilio’s funeral, packed the .38 and .380 guns he borrowed from old friends and, soaked in liquor, killed the men allegedly responsible for shooting Emilio in the chest in 2008.

It would have been just another homicide in the South Side of Chicago, where violent, often gang-related, retribution killings fuel the rising homicide rate. In 2007, the year before Torres returned home a total of 448 murders took place. In 2008, homicides in the city rose to 513—more than one killing per day.

While most people saw these murders as inevitable, Dr. Slutkin, a physician and professor of epidemiology and international health at the University of Illinois at Chicago School of Public Health, thought they could be prevented.

In 2000, he started Ceasefire Chicago, using what he knew from studying infectious diseases in Africa. The idea was to look at violence, especially gang and drug-related violence, as a transmittable disease. Like preventing a death from an infectious disease, preventing a death from homicide would not only save a life, but it would decrease the likelihood that more homicides would occur. In other words, it would stop “the infectious spread” of homicides.

The Ceasefire Chicago project, now known as Cure Violence, represents a new approach to a problem that is typically attacked through tougher sentencing and more policing. Proponents of this epidemiological approach to social ills say that society is currently structured to “treat” or “quarantine” the problem of violence and homicide after it occurs by incarcerating criminals associated with violent crime and murders, such as gang members or drug offenders.

But, as with outbreaks of infectious diseases, Dr. Slutkin says we can take preventative approaches by using known disease models to identify the conditions under which violence spreads, preventing an outbreak of even more violence.

The model is especially useful for gang violence, says Dr. Slutkin, who found that former gang members could act as “interrupters” who could diffuse conflicts like Torres’s planned murder, in order to keep one act of violence or homicide from begetting another.

Ceasefire identified Zale Hoddenbach, an old friend of Torres, as a potential interruptor and Hoddenbach talked Torres out of killing his nephew’s assailants. The organization believes this prevented further shootings or killings that may have resulted from Torres’ retribution.

The study of disease has long taken into account how social factors, such as socioeconomic status and neighborhood crime put people at greater risk of disease, but the idea that homicide and other social problems like incarceration are diseases has only recently been used as a way to tackle these problems.

“I think it’s an interesting way to look at it—to turn homicide on its head and not look at it as something deviant people do and catch the deviant people in order to stop it,” said Dr. April Zeoli, an assistant professor at the School of Criminal Justice at Michigan State University and a trained epidemiologist. “If we look at it as a societal issue, where we have that source of infection, mode of transmission and susceptible population, then we can potentially come to new answers.”

Of course, there is no pathogenic homicide virus that can contagiously jump from one person to the next, but homicide may move on a map the way that a virus would.

“Violent activity predicts the next violent activity like HIV predicts the next HIV and TB [tuberculosis] predicts the next TB,” Dr. Slutkin has said.

Incarceration in America follows similar patterns, according to Dr. Ernest Drucker, an emeritus professor of family and social medicine at Montefiore Medical Center/Albert Einstein College of Medicine and an adjunct professor of epidemiology at Columbia University’s Mailman School of Public Health.

In his book, A Plague of Prisons, Dr. Drucker applies public health analysis usually reserved for epidemics like the flu, tuberculosis, AIDS and other diseases to demonstrate how incarceration takes on the characteristics of an infectious epidemic by moving through particular populations with self-perpetuating virulence.

“It started as a metaphor, but I realized, researching the book, that this really does look like an epidemic. It does meet the criteria,” he said at a recent talk at Columbia University.

Like many epidemics, mass incarceration is rampant in the poorest neighborhoods of America’s cities, affecting young minority men, primarily black and Hispanic. In some communities, 90 percent of families have members who have been incarcerated. Like a hereditary disease, children of an imprisoned parent have lower life expectancy. It is also six to seven times more likely that they will be put in prison compared to children of families not affected.

Dr. Zeoli has taken this approach a step further than a mere analogy, by mapping, or geocoding, the physical and temporal movement of Newark homicides on record the way epidemiologists map infectious diseases like cholera or HIV. The study was published in the journal Justice Quarterly.

She and her colleagues, Jesenia M. Pizarro, Sue C. Grady and Christopher Melde, geocoded every homicide documented by Newark Police Department’s Homicide Unit in Newark, N.J. from January 1982 to September 2008 and viewed their movement on a map.

They were surprised to find that, by comparing the maps of homicides overall to gun- and gang-related homicides, the “infection”—increased homicides—arrived even before the homicide clusters linked to guns or gangs, the proposed “infectious agent.”

This could mean that something other than gang or gun violence—which criminal justice analysts often blame—was initially at work in propelling the spread. Dr. Zeoli and her colleagues suspect that socioeconomic realities, like poverty or poor community infrastructure, may play a bigger role.

Dr. Zeoli’s ongoing study explores the possibility that socioeconomic status may better predict homicide movement, providing a promising alternative to those who see harsh policing and strict sentencing as anachronistic. To be sure, the application of epidemiology to these topics comes with complications that are similar to those that come with studying true diseases. Finding accurate data and interpreting trends is still quite difficult.

And, unlike an infectious disease, it is much more difficult to isolate a cause for homicide, violence or imprisonment.

But those who take the social ills as disease approach say its value is in identifying prevention measures.

Dr. Drucker, points to proposals to reform sentencing laws and programs that decrease recidivism, or reentry into prison, such as the Goldman Sachs funded Osborne Association in New York. In addition, Dr. Drucker says, changing drug-laws in order to decriminalize drug addiction—considered an actual disease in the DSM (Diagnostic and Statistical Manual of Mental Disorder)—could also prevent incarceration.

“If we can dig down and discover what that source is, what that mode of transmission looks like, who that susceptible population is, and what population is resistant and why,” said Dr. Zeoli, “then we can really use those principles of infectious disease prevention or control to halt the spread of homicide or different types of violence.”

Detractors argue it is not clear whether the preventative approach is working.

Although Ceasefire Chicago has taken credit for the drop in homicides in areas where the organization was operating, Tracy Siska, a writer for the blog, proposed that other factors were occurring at the same time, like new policing strategies, increased incarceration and national drops in crime, which may have had a greater role in the reported decreases in crime, than the  interrupter’s work.

Social ills do not have one single cause and are not going to be stopped through one form of prevention. But, for Dr. Drucker, the approach provides an alternative to what he says have been largely ineffective measures used thus far and also ensures that “public health people are in the room when governments make decisions.”

Edited by Elaine Meyer. Additional research by Lauren Weisenfluh.

Article originally posted on, an online publication sponsored by the Department of Epidemiology at Columbia University. 2×2 aims to inform the health conversation through timely and effective communication of emerging public health science.