most at risk if the pump were to blame. Just as his theory suggested,
this was also where most cases were appearing.
Snow would never live to see his ideas vindicated. When he died
in 1858, The Lancet published a two-sentence obituary, which failed
to mention his work on outbreaks. Like an intellectual miasma, the
concept of bad air continued to linger in the medical community.
Eventually the idea of contagious cholera did catch on. By the
early 1890s, many had come to accept Robert Koch’s notion of
germs that spread disease. Then, in 1895, Koch managed to infect a
laboratory animal with cholera.[6] His postulates fulfilled, it was
convincing evidence that bacteria was causing the disease, and that
cholera was spreading through infected water rather than coming
from bad air. Snow had been right.
W infectious diseases in terms of germs rather
than miasma, but Gary Slutkin argues that we haven’t made the
same progress in our analysis of violence. ‘We’re very stuck in
moralism – who’s good, who’s bad.’ He points out that many societies
are highly punitive; they haven’t really shifted in their attitudes to
violence for centuries. ‘I really feel like I’m living in the past.’
Although biology has moved on from the idea of bad air, debate
around crime still focuses on bad people. Slutkin thinks this is in part
because contagious violence is less intuitive than disease. ‘Here you
don’t actually have an invisible microorganism that you can at least
show somebody under the microscope.’ However, the parallels
between infectious disease and violence seemed clear to him. ‘I
remember an epiphany when I asked someone “what’s the greatest
determinant of violence? What’s the greatest predictor?” And the
answer was “a preceding violent event”.’ In his mind, it was an
obvious sign of contagion. Which made him wonder: perhaps
methods used to control infectious diseases could be applied to
violence too?
There are several similarities between outbreaks of disease and
violence. One is the lag between exposure and symptoms. Just like
an infection, violence can have an incubation period; we might not
see symptoms straight away. Sometimes a violent event will lead to