Super-spreaders of novel coronaviruses that cause SARS, MERS and COVID-19: a systematic review

Abstract

Purpose: Most index cases with novel coronavirus infections transmit disease to just one or two other individuals, but some individuals "super-spread"-they infect many secondary cases. Understanding common factors that super-spreaders may share could inform outbreak models, and be used to guide contact tracing during outbreaks.

Methods: We searched in MEDLINE, Scopus, and preprints to identify studies about people documented as transmitting pathogens that cause SARS, MERS, or COVID-19 to at least nine other people. We extracted data to describe them by age, sex, location, occupation, activities, symptom severity, any underlying conditions, disease outcome and undertook quality assessment for outbreaks published by June 2021.

Results: The most typical super-spreader was a male age 40+. Most SARS or MERS super-spreaders were very symptomatic, the super-spreading occurred in hospital settings and frequently the individual died. In contrast, COVID-19 super-spreaders often had very mild disease and most COVID-19 super-spreading happened in community settings.

Conclusions: SARS and MERS super-spreaders were often symptomatic, middle- or older-age adults who had a high mortality rate. In contrast, COVID-19 super-spreaders tended to have mild disease and were any adult age. More outbreak reports should be published with anonymized but useful demographic information to improve understanding of super-spreading, super-spreaders, and the settings in which super-spreading happens.

Keywords: Coronavirus; Heterogeneity of transmission; Index cases; Super-spreading.

Figure 1

Study selection procedure.

Figure 2

Quality assessment scores for epidemiologic information on nCoV super-spreaders. Note: Questions in Table 1 were used to determine the quality assessment scores shown in Figure 2. nCoV, novel coronavirus.

Figure S4

Age distribution of super-spreader cases compared to concurrent proportion of population in each age group in China. Note: All super-spreader individuals are counted here but the population proportions in each age group are only for China in 2003 and 2020 because China contributed most of the age-specific data for either SARS or COVID super-spreaders detailed breakdown or comparison for each contributing country is not informative when ages were generally unavailable outside of China. Chinese Population distribution source: https://www.populationpyramid.net/china.