Clustering and superspreading potential of SARS-CoV-2 infections in Hong Kong

Nat Med. 2020 Nov;26(11):1714-1719. doi: 10.1038/s41591-020-1092-0. Epub 2020 Sep 17.


Superspreading events (SSEs) have characterized previous epidemics of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) infections1-6. For SARS-CoV-2, the degree to which SSEs are involved in transmission remains unclear, but there is growing evidence that SSEs might be a typical feature of COVID-197,8. Using contact tracing data from 1,038 SARS-CoV-2 cases confirmed between 23 January and 28 April 2020 in Hong Kong, we identified and characterized all local clusters of infection. We identified 4-7 SSEs across 51 clusters (n = 309 cases) and estimated that 19% (95% confidence interval, 15-24%) of cases seeded 80% of all local transmission. Transmission in social settings was associated with more secondary cases than households when controlling for age (P = 0.002). Decreasing the delay between symptom onset and case confirmation did not result in fewer secondary cases (P = 0.98), although the odds that an individual being quarantined as a contact interrupted transmission was 14.4 (95% CI, 1.9-107.2). Public health authorities should focus on rapidly tracing and quarantining contacts, along with implementing restrictions targeting social settings to reduce the risk of SSEs and suppress SARS-CoV-2 transmission.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • COVID-19 / epidemiology*
  • COVID-19 / transmission*
  • Carrier State / epidemiology
  • Cluster Analysis
  • Contact Tracing
  • Female
  • Health Policy
  • Hong Kong / epidemiology
  • Humans
  • Male
  • Models, Theoretical
  • Pandemics
  • Patient Isolation / legislation & jurisprudence
  • Public Health / legislation & jurisprudence
  • Quarantine / legislation & jurisprudence
  • SARS-CoV-2 / physiology
  • Travel-Related Illness