Super-spreaders: a historical review.

The term super-spreader is used for multiple, and sometimes even conflicting, purposes. The reasons for this can be traced back to its complex history. Forerunners of the super-spreader concept-in discussions of so-called dangerous carriers and in analyses of explosive outbreaks during the early 20th century-revolved primarily around gastrointestinal diseases, not respiratory ones. In 1957-58, the H2N2 influenza pandemic and Wells and Riley's studies on tuberculosis drew attention to both the viability of airborne transmission and the existence of significant heterogeneity in infectivity. The term super-spreader was coined in 1972, in relation to computer simulations of influenza epidemics. Initially, super-spreaders were simply an additional feature within stochastic models of epidemics, with little effect on an epidemic's eventual course. The term was later appropriated to explain why outbreaks of airborne diseases continued in vaccinated populations, defying the predictions of contact-transmission-based models. The content and meaning of the term continued to fluctuate, from the mathematical characterisation of sexually active people with gonorrhoea, through HIV carriers with highly infectious semen, to central nodes within a network. This Historical Review reconstructs the historical growth of the concept of super-spreading, and offers insight into its current, highly diversified use.