How the latest COVID-19 cluster revealed loopholes in contact tracing: the K11 Musea outbreak

With at least 49 confirmed cases, the cluster related to Mr Ming’s Chinese Dining at K11 Musea in Tsim Sha Tsui has become the latest large-scale cluster in the fourth wave of local infections, while at the same time revealing loopholes in the SAR’s attempt to improve contact tracing through the self-developed app ‘Leave Home Safe’.

A 72-year old cleaner at the restaurant is suspected to be the index patient that caused the spread in the restaurant, Hong Kong health authorities said. While the cleaner had a mask on while working, droplets could remain in the air for some time, Dr Chuang Shuk-kwan, head of the Centre for Health Protection’s (CHP) communicable disease branch said.

While the cross-infection between used utensils in the eatery’s pantry could be a possible transmission method, the restaurant’s fresh air supply was only a third of the required standard, contributing to short-distance transmission, said government pandemic adviser Yuen Kwok-yung after inspecting the site. 

K11 Musea is closed until March 5 as the management carries out complete sterilisation in the mall after a 49-people cluster broke out in Mr Ming’s Chinese Dining. Photo by Sharon Abratique

Shortly after, the K11 Musea management said that they have decided to terminate the tenancy with Mr Ming’s Chinese Dining, as they looked into the issue and discovered that the fresh air supply was “below license requirement”. 

As the second-generation transmission extended to workers from other stores in the same mall, like Cartier and restaurant Lilium by Gitone, concerns regarding the ventilation system arose. K11 Musea’s spokesperson clarified that the restaurant had a separate ventilation system that is not connected to other shops and restaurants, highlighting that the mall has a ventilation system “close to the highest standards used in hospitals”. 

Visitors to the stores at K11 Musea who have used the government-developed coronavirus risk-exposure app have been notified that they should get tested as soon as possible, while previously only people who had been to Mr Ming’s Chinese Dining and scanned the QR code would be notified. 

The Leave Home Safe app is supposed to notify users if they have been in the same venue with a patient, but the authorities have yet to trace back all relevant persons. Photo from Leave Home Safe website

However, the health authorities are unable to trace back around 10 customers who had lunch at the restaurant on February 19. Chuang mentioned that the person who picked up the phone that was left on the information sheet does not correspond with the name on the same sheet, as some of these customers left their contact details on paper, rather than using the Leave Home Safe app. 

The effectiveness of using Leave Home Safe as a method to curb transmission is doubted, as it only provides retrospective reminders that the user has been exposed to a high-risk environment. Dr Albert Au, Principal Medical and Health Officer at the Communicable Disease Branch at the CHP responded at a press briefing that the CHP can locate some close contacts to send to quarantine, or discover that some visitors have forgotten that they had visited the restaurant, therefore he thinks that the app is useful on a broader perspective. 

However, Au did not directly respond whether the app is effective in curbing transmission, and only remarked that the app has its limitations, such as the identity of the person who scanned the QR code, and the number of people in accompaniment, therefore the authorities are having difficulty with tracing and contacting every customer that visited the restaurant on February 19, in which there are around 70 people in total. He believes that relevant government departments will ‘enhance’ the application.

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