Accepted for/Published in: Journal of Medical Internet Research
Date Submitted: Dec 19, 2020
Date Accepted: Mar 19, 2021
Date Submitted to PubMed: Apr 16, 2021
Evolving epidemiological characteristics of COVID-19 in Hong Kong, January to August 2020
ABSTRACT
Background:
COVID-19 plagued the globe, with non-pharmaceutical interventions and multiple SARS-CoV-2 clusters hinting on its evolving epidemiology.
Objective:
To guide interventions, we studied such evolvement in Hong Kong in January-August 2020. We focused on containment delays (CDs) and serial intervals (SIs).
Methods:
We retrieved the official case series and the Apple mobility data. The empirical CDs and SIs were fitted to theoretical distributions, and multivariate linear regression models were used to examine their associated factors. Effective reproductive number (Rt) was estimated with the best fitted distribution for SIs.
Results:
We identified two epidemic waves, featured by imported cases and clusters of local cases respectively. Rt rose to peak at 2.39 (wave 1) and 3.04 (wave 2) respectively. Log-normal distribution best fitted the 1574 CDs (mean:5.18 days; SD:3.04) and the 558 SIs (17 negative) (mean:4.74 days; SD:4.24). CDs increased with older age (≥60 years) (aOR:1.10; 95%CI:1.03,1.17), but decreased with general symptoms (aOR:0.89; 95%CI:0.85,0.94), involvement in a cluster (aOR:0.82-0.91) or detection in the public healthcare sector (aOR:0.76; 95%CI:0.72,0.80). SIs were shorter in wave 2 (aOR:0.79; 95%CI:0.72,0.86) and in tertiary transmission or beyond (aOR:0.68-0.89), but was lengthened by mobility (aOR:1.01; 95%CI:1.00,1.01).
Conclusions:
Pre-symptomatic transmission and asymptomatic cases reminded the importance of remaining vigilant about COVID-19. The time-varying epidemiological parameters suggest the need to incorporate their temporal variations when depicting the epidemic trajectory. The slowing-down of the epidemic in late August 2020 suggested prompt government actions were crucial in suppressing resurgence. Clinical Trial: Not applicable
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