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

• Published in: Nature Medicine Vol. 26; no. 11; pp. 1714 - 1719
• Main Authors: Adam, Dillon C., Wu, Peng, Wong, Jessica Y., Lau, Eric H. Y., Tsang, Tim K., Cauchemez, Simon, Leung, Gabriel M., Cowling, Benjamin J.
• Format: Journal Article Magazine Article
• Language: English
• Published: New York Nature Publishing Group US 01.11.2020; Nature Publishing Group
• Subjects: 692/699/255; 692/700/478/174; Biomedical and Life Sciences; Biomedicine; Cancer Research; Carrier State - epidemiology; Cluster Analysis; Clustering; Confidence intervals; Contact Tracing; Coronaviridae; Coronaviruses; COVID-19; COVID-19 - epidemiology; COVID-19 - transmission; Disease transmission; Distribution; Female; Health Policy; History; Hong Kong - epidemiology; Households; Humans; Infectious Diseases; Letter; Life Sciences; Male; Metabolic Diseases; Models, Theoretical; Molecular Medicine; Neurosciences; Pandemics; Patient Isolation - legislation & jurisprudence; Public health; Public Health - legislation & jurisprudence; Quarantine - legislation & jurisprudence; Respiratory diseases; SARS-CoV-2 - physiology; Severe acute respiratory syndrome coronavirus 2; Travel-Related Illness; Viral diseases; Hong Kong; Hong Kong, China; Hong Kong China; China
• ISSN: 1078-8956; 1546-170X; 1546-170X; 1744-7933
• DOI: 10.1038/s41591-020-1092-0

Superspreading events (SSEs) have characterized previous epidemics of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) infections 1 – 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-19 7 , 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. Cases linked to superspreading events are estimated to account for 80% of all local transmission of SARS-CoV-2 in Hong Kong in a study with implications for public health policies.