According to Tia Ghose, new research suggests that murder is contagious and may spread like the flu. In this study, the researchers relied on the same techniques public-health officials use to track the spread of diseases, but applied them to the spread of homicide in Newark, N.J., over a 26-year span from 1982 to 2008. Just as in other epidemics, certain neighborhoods were more susceptible than others. Diverse, immigrant-rich communities looked to be protected against homicide’s spread in the research, while the poorest neighborhoods were more vulnerable. These findings suggest communities could inoculate themselves against murder waves by addressing the underlying risk factors.