Complementing Contact Tracing with Mass Testing for Successful Containment of Beta Variant COVID-19 (SARS-CoV-2 VOC B.1.351) Outbreak in Hong Kong

An imported case (M/28) from the Philippines stayed in the adjacent room with Case 1 at the quarantine hotel for 13 days (March 25, 2021 to April 6, 2021). Whole genome sequencing showed that this imported case was the ancestor of the community outbreak of SARS-CoV-2 VOC B.1.351 in Hong Kong.

Since the 120 people staying in the residential building of the first 2 cases of SARS-CoV-2 VOC B.1.351 (cases 1 and 2) were not infected during the quarantine period, the non-domestic resident would be subject to compulsory tests on the 3rd, 7th, 12th and 19th day after the isolation of the confirmed case of SARS-CoV-2 COV B.1.351 without epidemiological source. Quarantine of all residents of the residential building for 21 days would be applied if there was more than one case of SARS-CoV-2 COV B.1.351 with no epidemiological link.

Social gathering of Cases 3, 6, 7, 9, 10 and 11 in Case 9’s apartment (No. 37 Fuk Wing Street) with drinking on April 18, 2021.

Mandatory testing for COVID-19 could be waived for HDDs who had received two doses of COVID-19 vaccine for 14 days.

Social gathering of Cases 3, 6, 7, 9, 10 and 11 in Case 9’s apartment (No. 37 Fuk Wing Street) with drinking on April 18, 2021.

Social gathering of Cases 3, 6, 7, 9, 10 and 11 in Case 9’s apartment (No. 37 Fuk Wing Street) with drinking on April 18, 2021.

Social gathering of Cases 1, 2, 8, 9, 10 and 11 in Case 8’s apartment (Fung Hing House, Hing Wah II Estate) without drinking on April 13, 2021 but Cases 1 and 2 did not disclosed this information only on May 5, 2021. Therefore, contact tracing could not be performed in time for the identification of cases 8, 9, 10 and 11.

The case was identified retrospectively when cases 1 and 2 revealed the events of the social gathering.

Social gathering of Cases 3, 6, 7, 9, 10 and 11 in Case 9’s apartment (No. 37 Fuk Wing Street) with drinking on April 18, 2021.

Social gathering of Cases 1, 2, 8, 9, 10 and 11 in Case 8’s apartment (Fung Hing House, Hing Wah II Estate) without drinking on April 13, 2021 but Cases 1 and 2 did not disclosed this information only on May 5, 2021. Therefore, contact tracing could not be performed in time for the identification of cases 8, 9, 10 and 11.

The case was identified retrospectively when cases 1 and 2 revealed the events of the social gathering.

Cases 3, 6, 7, 9, 10 and 11 social gathering at Case 9’s apartment (No. 37 Fuk Wing Street) with drinking on April 18, 2021.

Social gathering of Cases 1, 2, 8, 9, 10 and 11 in Case 8’s apartment (Fung Hing House, Hing Wah II Estate) without drinking on April 13, 2021 but Cases 1 and 2 did not disclosed this information only on May 5, 2021. Therefore, contact tracing could not be performed in time for the identification of cases 8, 9, 10 and 11.

The case was identified retrospectively when cases 1 and 2 revealed the events of the social gathering.

Cases 3, 6, 7, 9, 10 and 11 social gathering at Case 9’s apartment (No. 37 Fuk Wing Street) with drinking on April 18, 2021.

Social gathering of Cases 1, 2, 8, 9, 10 and 11 in Case 8’s apartment (Fung Hing House, Hing Wah II Estate) without drinking on April 13, 2021 but Cases 1 and 2 did not disclosed this information only on May 5, 2021. Therefore, contact tracing could not be performed in time for the identification of cases 8, 9, 10 and 11.

The case was identified retrospectively when cases 1 and 2 revealed the events of the social gathering.