Superspreading event

A superspreading event (SSEV) is an event in which an infectious disease is spread much more than usual, while an unusually contagious organism infected with a disease is known as a superspreader. In the context of a human-borne illness, a superspreader is an individual who is more likely to infect others, compared with a typical infected person. Such superspreaders are of particular concern in epidemiology.

Some cases of superspreading conform to the 80/20 rule,^[1] where approximately 20% of infected individuals are responsible for 80% of transmissions, although superspreading can still be said to occur when superspreaders account for a higher or lower percentage of transmissions.^[2] In epidemics with such superspreader events, the majority of individuals infect relatively few secondary contacts.^{[citation needed]} The degree to which superspreading contributes to an epidemic is often quantified by the t₂₀ metric, which denotes the proportion of infections attributable to the most infectious 20% of the population.^[3]

SSEVs are shaped by multiple factors including a decline in herd immunity, nosocomial infections, virulence, viral load, misdiagnosis, airflow dynamics, immune suppression, and co-infection with another pathogen.^[4]