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.