Baltimore police say they can't explain the recent uptick in homicides in the city's Northeast District, which has seen more murders than any other part of the city so far this year. The killings seem disturbingly random, ranging from domestic disputes and arguments among neighbors to drug- and gang-related violence. Last month, for example, a man killed his neighbor and a bystander during an argument over a parking space. Several murders appear to have been the result of gang disputes. And for some of the killings police can cite no motive at all.

The murders are seemingly unrelated, yet they resemble what in another context we would see as a pattern: Individual acts of violence expand outward much as cases of infectious disease do. A school of thought in criminal justice research posits that even though gun violence may not be a physical illness like cholera or smallpox, it does behave as if it were contagious. One or two acts of violence initiate a ripple effect that can spread through a community and spark similar crimes among people who had no connection to the original incident.

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This is as good an explanation as any for what is currently happening in Northeast Baltimore. But the comparison also suggests that viewing gun violence through the lens of the infectious disease model could have important implications for how authorities seek to quell the homicide epidemic there.

The idea that violence behaves like an infectious agent is often attributed to Dr. Gary Slutkin, a physician who spent many years studying disease outbreaks in Africa. After his return, Dr. Slutkin noticed that outbreaks of gun violence in the U.S. bore an uncanny resemblance to infectious disease epidemics such as tuberculosis and H.I.V. Both seem to occur in clusters and spread in waves, and the pathways of transmission for both run from one person to another. Just as people exposed to the Ebola virus are likely to develop the illness, people who witness or are victimized by violence are more likely to act violently themselves.

Dr. Slutkin theorized that exposure to violence affects the brain in ways that make people more susceptible to recreating those traumatic experiences in their own lives. The neural pathways through which that process occurs are not well understood, but the hypothesis suggests that epidemic levels of gun violence may have more in common with public health models of disease control than with traditional law-enforcement procedures.

Whether one views the relationship between violence and infectious disease literally or metaphorically, the conclusion should be the same. It is much better to prevent an outbreak than to contain it. But how do you immunize a community against violence? Police have beefed up patrols in the Northeast District, and their presence there is essential for deterring crime. But obviously they can't be everywhere all the time, and because police are sometimes required to use force themselves, they can inadvertently foster a culture of violence even when their acts are morally and legally justified to protect themselves and others.

What's needed in addition is a preventive strategy against gun violence that's analogous to inoculating communities against measles or influenza. Some people may still get the "disease" but they can't easily pass it on to others if the broader population isn't susceptible, and if enough people clustered in the outbreak's hot spots are protected from further exposure, eventually the "infectious" agent gets stopped in its tracks.

That's the kind of intervention envisioned by Baltimore's Safe Streets program, which sends highly trained outreach workers and street-smart "violence interrupters" into troubled neighborhoods to mediate disputes and head off conflicts by persuading the relatively small number of people who are most likely to become perpetrators or victims of gun crimes to alter their risky behaviors. Encouraging such high-risk individuals to settle differences peacefully can interrupt the cycle of violence and significantly diminish the chances of it infecting others. It also complements the deterrent role played by police in keeping communities safe.

But despite efforts at expansion, Baltimore's Safe Streets program is still woefully under-resourced and under-staffed. Of the city's 27 police posts, only two have a full complement of workers — director, deputy director, three outreach workers and two "violence interrupters" — and neither of them are located in Northeast Baltimore. Mayor Stephanie Rawlings-Blake and City Police Commissioner Anthony Batts need to make installing a strong Safe Streets presence in Northeast a top priority because time is of the essence; like any epidemic, the longer authorities wait to intervene in the spreading violence, the harder it will be to stop. The police have a vital role to play in creating the conditions for a successful intervention, but they can't do it all on their own.

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