Clustering and superspreading potential of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Hong Kong
Superspreading events have characterised previous epidemics of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) infections. Using contact tracing data, we identified and characterized SARS-CoV-2 clusters in Hong Kong. Given a superspreading threshold of 6-8 secondary cases, we identified 5-7 probable superspreading events and evidence of substantial overdispersion in transmissibility, and estimated that 20% of cases were responsible for 80% of local transmission. Among terminal cluster cases, 27% (45/167) ended in quarantine. Social exposures produced a greater number of secondary cases compared to family or work exposures (p<0.001) while delays between symptom onset and isolation did not reliably predict the number of individual secondary cases or resulting cluster sizes. Public health authorities should focus on rapid tracing and quarantine of contacts, along with physical distancing to prevent superspreading events in high-risk social environments.
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It would be helpful for an international audience to describe the methodology of contract tracing. How well were contacts of asymptomatic contacts traced? What is the risk that spread via asymptomatic contact of asymptomatic contact was attributed erroneously to a symptomatic person? If that risk was high, clusters thought to be due to super spreader events might have actually been a collection of clusters of spread by asymptomatic contacts. What are the other limitations of this methodology?
Posted 21 May, 2020
On 17 Sep, 2020
Clustering and superspreading potential of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Hong Kong
Posted 21 May, 2020
On 17 Sep, 2020
Superspreading events have characterised previous epidemics of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) infections. Using contact tracing data, we identified and characterized SARS-CoV-2 clusters in Hong Kong. Given a superspreading threshold of 6-8 secondary cases, we identified 5-7 probable superspreading events and evidence of substantial overdispersion in transmissibility, and estimated that 20% of cases were responsible for 80% of local transmission. Among terminal cluster cases, 27% (45/167) ended in quarantine. Social exposures produced a greater number of secondary cases compared to family or work exposures (p<0.001) while delays between symptom onset and isolation did not reliably predict the number of individual secondary cases or resulting cluster sizes. Public health authorities should focus on rapid tracing and quarantine of contacts, along with physical distancing to prevent superspreading events in high-risk social environments.
Figure 1
Figure 2
Figure 3
Figure 4
It would be helpful for an international audience to describe the methodology of contract tracing. How well were contacts of asymptomatic contacts traced? What is the risk that spread via asymptomatic contact of asymptomatic contact was attributed erroneously to a symptomatic person? If that risk was high, clusters thought to be due to super spreader events might have actually been a collection of clusters of spread by asymptomatic contacts. What are the other limitations of this methodology?