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Superspreading Event of SARS-CoV-2 Infection at a Bar, Ho Chi Minh City, Vietnam

Our take —

Using detailed epidemiologic, contact tracing, and genome sequencing data, a cluster of infections was identified with an apparent source of an indoor bar in Ho Chi Minh City on March 14, 2020. From the initial index case, a total of 18 additional cases were identified, including 12 who also attended the bar that evening. This event was characterized as a superspreading event, and genome sequencing data confirms these clusters as likely being part of the same, single cluster. Without adequate precautions, indoor bars with poor ventilation and prolonged contact between patrons may be the site of superspreading events.

Study design

Case Series

Study population and setting

This study presents findings on an identified case of COVID-19 in Ho Chi Minh City, Vietnam on March 18, 2020 and the contact tracing data related to this case. The contact tracing data identifies a likely superspreading event, defined as between six and eight secondary cases. Genetic sequencing was conducted in order to further establish whether the identified cases were from the same cluster.

Summary of Main Findings

The index patient was a 43-year old man who presented to the Hospital for Tropical Diseases with fever, cough, and other symptoms. Symptom onset was on March 17, 2020. He subsequently showed evidence of SARS-CoV-2 infection by RT-PCR. Based on the contact tracing data, the index patient had traveled between Thailand and Vietnam in the 14 days prior to symptom onset. He had attended an event at an indoor bar in Ho Chi Minh City on March 14. Based on contact tracing data, an additional 18 positive PCR-confirmed cases were identified (12 from the bar and 6 were other contacts). None of the confirmed cases reported any symptoms on March 14 or 15. Whole genome sequences of SARS-CoV-2 obtained from 11 of the confirmed cases were either identical of very similar, even when compared with other sequences from Ho Chi Minh City.

Study Strengths

Detailed contact tracing data and sequencing data provide strong evidence of a superspreading event that took place in an indoor bar.

Limitations

The total number of contacts of the initial case is not provided and therefore calculation of a secondary attack rate is not possible.

Value added

Results from this study provide further evidence that indoor bars with limited ventilation may be the site of superspreading events.

This review was posted on: 11 November 2020