- observed reproductive number (R) of 0.58 (95% CI: 0.45 – 0.71)

- dispersion parameter (k) of 0.45 (95% CI: 0.31 – 0.76)


University of Michigan - Ann Arbor

From the 539 infections that occurred in clusters, all 210 solely imported cases (38.9%) were excluded from subsequent analysis due to uncertainties concerning transmission within each cluster whilst overseas. Within the remaining 53 clusters initiated by a local or imported infection, 245 (245/329; 74.5%) could be linked resulting in 171 unique infector-infectee transmission pairs with 94 unique infectors. 

Given a superspreading threshold of 6-8 secondary cases, 2-4 SSEs were directly observed where the source was known. Likelihood analysis based on final cluster sizes increased the estimate of R to 0.75 (95% CI: 0.6 – 0.96) and decreased estimates of k to 0.37 (95% CI: 0.16 – 1.16). Based on these estimates we determined a coefficient of variation of 2.5 and inferred that approximately 20% of SARS-CoV-2 infections are responsible for 80% of all transmission events in Hong Kong.

Transmission Pairs & Individual variation in SARS-CoV-2 transmission

Dillon Adam, Peng Wu, Jessica Wong et al. Clustering and superspreading potential of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Hong Kong, 21 May 2020, PREPRINT (Version 1) available at Research Square [+https://doi.org/10.21203/rs.3.rs-29548/v1+]
https://www.researchsquare.com/article/rs-29548/v1

Clustering and superspreading potential of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Hong Kong

- median serial interval was 4 days (IQR 3 – 8 days)

- mean of the fitted normal distribution was 5.6 days (standard deviation 4.3 days)

- observed at least eight instances of likely pre-symptomatic transmission where symptom onset of the infectee preceded that of the infector by one day (N=2) or occurred on the same day (N=6)

-thirty-four unique infectors (35/94; 37.2%) were linked to two or more secondary cases, and the largest number of individual secondary cases was 11

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