Abstract
BackgroundCOVID-19, caused by SARS-CoV-2, first appeared in China and subsequently developed into an ongoing epidemic. Understanding epidemiological factors characterising the transmission dynamics of this disease is of fundamental importance.AimsThis study aimed to describe key epidemiological parameters of COVID-19 in Hong Kong.MethodsWe extracted data of confirmed COVID-19 cases and their close contacts from the publicly available information released by the Hong Kong Centre for Health Protection. We used doubly interval censored likelihood to estimate containment delay and serial interval, by fitting gamma, lognormal and Weibull distributions to respective empirical values using Bayesian framework with right truncation. A generalised linear regression model was employed to identify factors associated with containment delay. Secondary attack rate was also estimated.ResultsThe empirical containment delay was 6.39 days; whereas after adjusting for right truncation with the best-fit Weibull distribution, it was 10.4 days (95% CrI: 7.15 to 19.81). Containment delay increased significantly over time. Local source of infection and number of doctor consultations before isolation were associated with longer containment delay. The empirical serial interval was 4.58–6.06 days; whereas the best-fit lognormal distribution to 26 certain-and-probable infector–infectee paired data gave an estimate of 4.77 days (95% CrI: 3.47 to 6.90) with right-truncation. The secondary attack rate among close contacts was 11.7%.ConclusionWith a considerable containment delay and short serial interval, contact-tracing effectiveness may not be optimised to halt the transmission with rapid generations replacement. Our study highlights the transmission risk of social interaction and pivotal role of physical distancing in suppressing the epidemic.
Highlights
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for coronavirus disease (COVID-19), first appeared in Wuhan, China, in early December 2019, where it caused an epidemic which subsequently spread to other countries
We summarised the characteristics of confirmed cases with descriptive statistics such as mean, median, range, standard deviation (SD) and frequency, 95% bootstrapped confidence interval and 95% binomial confidence interval
Two imported cases were intercepted at borders, and two other cases, including one imported and one who was a close contact of an imported case, were under quarantine during symptom onset
Summary
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for coronavirus disease (COVID-19), first appeared in Wuhan, China, in early December 2019, where it caused an epidemic which subsequently spread to other countries. After the first confirmed COVID-19 case was imported to Hong Kong on 22 January 2020 [5,6], the government promptly introduced multi-pronged interventions to suppress the spread of SARS-CoV-2 [7]. Such interventions included physical distancing (school closures, work-from-home arrangements for civil servants, suspension of public leisure and recreational facilities) and border restriction. The empirical serial interval was 4.58–6.06 days; whereas the best-fit lognormal distribution to 26 certain-and-probable infector–infectee paired data gave an estimate of 4.77 days (95% CrI: 3.47 to 6.90) with right-truncation. Our study highlights the transmission risk of social interaction and pivotal role of physical distancing in suppressing the epidemic
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Schedule a callMore From: Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin
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