The epidemiology of COVID-19 cases and the successful containment strategy in Hong Kong–January to May 2020

Abstract

Background: Hong Kong, a Special Administrative Region of China, recorded its first confirmed coronavirus disease 2019 (COVID-19) case on 23 January 2020. We reviewed the case epidemiology and the various public health measures implemented from January to May 2020. Methods: The epidemiological and clinical characteristics of the cases recorded in different phases of the epidemic were described and compared, and the effectiveness of the public health measures implemented were reviewed using the changes in the daily number of confirmed cases and the interval from symptom onset to hospital admission. Results: Between January and May 2020, 1084 confirmed COVID-19 cases were reported, about 70% of which had a history of travel during the incubation period. The case fatality ratio was 0.4%. The local epidemic progressed through four phases: (1) preparedness and imported infection from mainland China, (2) local transmission, (3) imported infection from overseas countries associated with local transmission, and (4) controlled imported infection with limited local transmission, with an eventual reduction of the daily case number and minimization of the onset-to-admission interval. Various public health measures, including enhanced surveillance, border control, and social distancing, were introduced in phases in response to the prevailing local and global situations. Discussion: The overall containment strategy in Hong Kong led to a stabilization of the number of cases and the absence of a community-wide outbreak during the 4.5 m after the first case was reported. This strategy of containment might serve as an example for future planning of preparedness and response against novel infectious agents.

Settings of virus exposure and their implications in the propagation of transmission networks in a COVID-19 outbreak

“…The relatively short cascades of most transmission networks might have resulted from the government's system of contact tracing and quarantine, and early introduction of social distancing measures. [16 , 30] The analyses shown in this study could therefore be the result of both setting-based transmission and also the effects of intervention. Extrapolation to other cities/countries and at different epidemic stage would need to be cautioned.…”

“…Between 23 January and 19 June 2020, a total of 1128 cases of SARS-CoV-2 infection were reported in Hong Kong. The distribution of cases by reporting channels followed the description in a published report [16] . Travel restrictions were introduced by the government since January/February, and enhanced in addition to legal regulations on social distancing enacted (see Fig.…”

“…In Hong Kong, a 7·5-million population Asia-pacific metropolitan city, the first case of COVID-19 was reported in late January 2020, a month after the virus first detected in Wuhan, China [16] . Corresponding with the growth of the epidemic in Europe and USA, imported infections were increasingly detected as from February, which precipitated the occurrence of local outbreaks.…”

High Probability of Long Diagnostic Delay in Coronavirus Disease 2019 Cases with Unknown Transmission Route in Japan

“…The mean diagnostic delay between symptom onset and COVID-19 confirmation was approximately 6.3 days between the 9th and 11th week in Japan; it was longer than 6 days. The mean delay was shorter than 6 days in Shenzhen (4.6 days), Hong Kong (3.2 days), Korea (4.3 days), and Singapore (5.6 days) [ 15 , 16 , 17 , 18 ]. The figures could be influenced by censoring of date collection and definition of delay.…”

Travel-associated COVID-19: a challenge for surveillance?

“…The substantial morbidity and mortality associated with the pandemic led countries to implement exceptional public health measures, including stay-at-home recommendations and orders. In many countries, observed epidemiological patterns were similar and initially imported cases were soon followed by community transmission [2,3]. In countries that managed to control the local epidemics, reporting of cases continued at lower levels, with a large proportion of imported cases in some [4].…”