Suppressing COVID-19 transmission in Hong Kong: an observational study of the first four months

Abstract

Background: Hong Kong was one of the first locations outside of mainland China to identify COVID-19 cases in January 2020. We assessed the impact of various public health measures on transmission.Methods: We analysed data on all COVID-19 cases and public health measures in Hong Kong up to 7 May 2020. We described case-based, travel-based and community-based measures and examined their potential effects on case identification and transmission. Changes in transmissibility measured by the effective reproductive number Rt were estimated by comparing the Rt between periods when public health measures were and were not in effect. Delays in case confirmation in imported cases and locally infected cases were analysed to indicate the possible impact of expansion of laboratory testing capacity.Findings: Introduction of a 14-day quarantine on persons arriving from affected areas was associated with a 95% reduction in transmissibility from imported cases. Testing all arriving travelers reduced mean delays between arrival and detection of imported cases. Increases in laboratory testing capacity for pneumonia inpatients and symptomatic outpatients reduced the delay from onset to confirmation. Working from home and physical distancing measures implemented in high-risk facilities were associated with 67% and 58% reductions in transmission of COVID-19, respectively.Interpretation: Suppression of COVID-19 transmission in the first pandemic wave in Hong Kong was achieved through integration of travel-based, case-based and community-based public health measures focusing on early case identification and isolation and physical distancing.

Epidemiological Investigation of the First 135 COVID-19 Cases in Brunei: Implications for Surveillance, Control, and Travel Restrictions

“…By the time the early physical distancing measures had been implemented, the Rt had reduced from 5.6 (ranging between 3.9 and 6.0) at the start to 2.2 (95% credible bands: 0.86, 5.0) by the seventh day (March 11). Our findings on the importance of the test, isolate, and trace approach are consistent with observational studies from Hong Kong 21 and Singapore. 22 …”

Mathematical modelling of the dynamics and containment of COVID-19 in Ukraine

“…This can be explained by a combination of mortality among 40-60-year olds, together with a reduction in the level of infection they are able to pass to older people, suggesting that promoting working from home and other ways of reducing work contacts appear to be the most efficient way of controlling the spread of infection in Ukraine, and minimising disease burden in terms of cases and deaths. This result is consistent with an earlier observation that working from home provided the largest contribution to reducing early cases of COVID-19 in Hong Kong 32 .…”

Clustering and superspreading potential of SARS-CoV-2 infections in Hong Kong

“…These results, however, should be interpreted in the context of constrained community transmission given the moderate levels of physical distancing practiced in Hong Kong, including school closures, some adults working at home, cancellation of mass gatherings, as well as improved hygiene and universal mask wearing, which exceeded 98% compliance from February onward 11,12 . In the absence of such policies it is possible that even greater levels of superspreading could be expected.…”

“…This untraceable fraction could be interpreted as an upper bound on the proportion of transmission arising from anonymous interactions, fomites and/ or aerosols. However, this finding may have to be restricted to the context of places similar to Hong Kong, where there is a widespread adoption of suppression measures 12 .…”