On the 10th floor of the University of ­Illinois’ school of public health, Dr Gary ­Slutkin points to a map of Chicago with dots showing where murders have taken place. Lake ­Michigan lies to the east, the north is mostly clear, but some areas of the south and the west, including ­Englewood, are covered in dots.

“It’s the same pattern on a map showing ­incidence of cholera in Bangladesh. It’s an infective process,” he says.

Slutkin, the managing director of Cure the Violence, is a doctor who specialises in infectious disease control and reversing epidemics who used to work for the World Health Organization. He thinks violence behaves like tuberculosis or Aids – and sees it as an infectious disease that can be stamped out by challenging and changing behavioural norms. Across the room a graph shows fatal shootings in Chicago over several years — a rollercoaster of peaks and troughs. “It’s the same curve for almost every city,” he explains. “It’s an epidemic curve.”

If gun violence is an infectious ­disease, then Chicago has the bug pretty bad. There were 506 gun murders last year, 16% more than in 2011. This year, so far, has been even worse; three ­people were shot dead on 1 January alone, and with 43 fatal ­shootings this January was the deadliest in ­decades. A few weeks ago, Shirley Chambers lost her fourth of four children to gun violence.

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