This paper incorporates some theoretical ideas from the study of the epidemiology of infectious illness into a model of worker absence. The paper then seeks to quantify such infection effects by examining a personnel dataset which allows us to track daily absence decisions of a group of industrial workers employed in the same factory. We find significant effects of our measure of sickness in the (rest of the) workforce on the absence probabilities of individual workers, and offer a suggestion on how this might be used by managers to gauge the extent of illness transmission within the workplace.