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WHAT SERIAL KILLERS AND EPIDEMICS HAVE IN COMMON

Monday, 30th of May 2011

Though it's often said that serial killers and diseases strike at random, a new study shows that they both kill victims in a predictable pattern. That's why the tools criminologists use to track serial killers can also pinpoint the location where an epidemic started.

When detectives track a serial killer, they create maps showing where the victims were found in order to generate a "geographic profile" that can reveal where the killer lives. They're able to do this because most serial killers tend to choose victims relatively close to home - but not too close. It's too expensive and difficult for most people to travel far from where they live, so that's why killers strike near their residences. At the same time, they rarely choose victims from their close neighbors. A geographic profile creates hot spots where the killer is likely to be found by identifying areas the killer hasn't struck, but which are still fairly near where victims were found.

It turns out that epidemics work the same way. But why would a disease create the same geographic profile as a serial killer?

Queen Mary University of London biologist Steven Le Comber and colleagues used geographic profiling to analyze a historic outbreak of cholera in London, and geographic profiling techniques were able to locate the exact wells where the disease broke out based on the locations of its dead victims. They did similar studies on outbreaks of malaria in Cairo (see map). In a study published last week, they explain their findings:

The methods underlying geographic profiling (GP) depend on two concepts, (i) distance decay and (ii) the buffer zone. Distance decay results from the fact that travel requires effort, time and/or money, and that most crimes thus tend to occur relatively close to the criminal's home; for example, 70% of arsons occur within two miles of a serial arsonist's home. Similar constraints operate in infectious disease epidemiology where the probability of transmission declines with distance from an infected host. The buffer zone, in criminology, is an area around the criminal's home in which offences are less likely, arising partly because of increases in detection risk related to reduced anonymity within the criminal's local neighborhood, and partly because the number of criminal opportunities increases with distance from home. The latter influence also occurs in biological systems: assuming suitable habitats are randomly dispersed throughout the surrounding area, then as the distance from the anchor point (usually a home or workplace) increases, the total number of suitable habitats increases.

If geographic profiling continues to work well at identifying other sources of disease outbreaks, it could prove invaluable in stopping pandemics before they start. One could imagine a future where health care workers use GP software to input and track the geographic locations of patients who've contracted deadly, communicable diseases. If an epidemic pattern begins to emerge, doctors could go straight to the source and administer antivirals or vaccines before the killer gets out of control. This will stop disease far more efficiently than trying to immunize everyone in a large geographical area.

In a release, Le Comber said:

Correctly applied, geographic profiling shows great promise as a useful component of policy relating to the control of a wide variety of infectious diseases . . . targeting of interventions like this is more efficient, environmentally friendly and cost effective than untargeted intervention.

Studying the way detectives target serial killers may eventually save us from microscopic murderers, too.

This item is at http://io9.com/5802697/what-serial-killers-and-epidemics-have-in-common

Read the full scientific article via International Journal of Health Geographics at

http://www.ij-healthgeographics.com/content/10/1/35/abstract

Ilustration by Domen Colja/Shutterstock