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(1/10) Just posted our new preprint on the successful suppression of first wave of #COVID19 in Hong Kong with @gmleunghku https://www.researchsquare.com/article/rs-34047/v1
(2/10) As of 7 May, there were 1,045 COVID-19 cases, mainly in March and April, the majority of these cases were actually infected outside Hong Kong (“imported cases”).
(3/10) Travel-related measures were critical to reduce importation of infections and then local spread. 14 day quarantine of arriving persons from affected areas since early February reduced onwards transmission by 95%.
(4/10) Test+trace has been used throughout the epidemic. Cases were identified in outpatients, inpatients, persons under medical surveillance, and arriving travellers. All cases, even asymptomatics, are isolated in hospital. Their close contacts are traced and quarantined.
(5/10) On average around 4 close contacts were traced for each case. Among thousands of quarantined contacts, 99 cases were identified in quarantine, indicating the value of this intervention in getting ahead of virus spread.
(6/10) In our other preprint on superspreading we reported just one example of a 'failure' of quarantine – a close contact was quarantined without symptoms but had already passed on infection to his wife (footnote 1 in Figure 3 of that preprint) https://www.researchsquare.com/article/rs-29548/v1
(7/10) Almost everybody in Hong Kong was wearing masks in public throughout the epidemic. But there was evidence of community spread in early March, despite this universal masking and test+trace.
(8/10) Community measures were important in suppressing transmission. Work-at-home was implemented for civil servants and many private businesses in February, stopped in March, and re-implemented later in March. We estimated this reduced transmission by 67% when in place.
(9/10) Quite a bit of transmission had occurred in bars and leisure facilities, we estimated that the closure of these in late March also reduced transmission by 58%.
(10/10) In combination, traveler quarantine, test+trace, face masks, and moderate physical distancing, all contributed to the successful suppression of #COVID19 in Hong Kong without needing to resort to a lockdown.
