Do some COVID-19 patients act as “superspreaders”?
The individual variation in the transmission of an infection is described by a factor called “dispersion factor or k ”. The lower “k” value, the more transmission comes from a small proportion of individuals acting like superspreaders. Superspreading clusters have been observed in past coronavirus outbreaks (SARS/MERS), where a small number of infected individuals was responsible for a large proportion of secondary transmissions, with an estimated “k” of about 0.16 for SARS and 0.25 for MERS.257 It is unclear whether superspreading clusters have contributed to the COVID-19 outbreak. A simulation of early outbreak trajectories estimated that “k ” for COVID-19 is higher than for SARS and MERS.257 However, in a recent preprint study, the estimate of “k ” for SARS-CoV-2 was around 0.1, suggesting that around 10% of infected patients may have been responsible for 80% of secondary transmissions.258 Individual variation in infectiousness is difficult to measure, as it is mostly empirical, but the identification of any SARS-CoV-2 superspreading will be of primary importance for pandemic control.