Outbreak Column 10: What Causes Outbreaks – Questions of Attribution

In healthcare infection control the ‘chain of infection’ is commonly used to describe disease transmission. The chain of infection suggests that for cross-infec­tion to result there is a: specific micro-organism, reservoir, way-out, mode of transmission, way-in and a susceptible host. In reality there are multiple options for each of these variables.

The chain of infection implies a single linear process from an organism to an infection in the way it shows as a series of interlocking links in a simple circle.

Essentially, the chain of infection is a template which can explain any individual infection transmission pathway; but it is not a model that permits the simultaneous illustration of multiple modes of transmission. This paper illustrates and discusses all the care setting transmission pathways that lead to infection and outbreaks in order to identify the outbreak critical elements.