Visualising Hong Kong’s biggest Covid-19 super-spreader event

The explosion of cases threw a spotlight on the niche social scene that many in the city knew little about before the outbreak.

Authorities warned of a “super-spreading” event centred on dance clubs across the city after the number of Covid-19 cases tied to such venues continued to grow.

The cluster has ballooned to 732 people – the largest in Hong Kong since the start of the pandemic – quickly eclipsing an outbreak linked to bars and musical performances in March that involved 103 people.

The cluster came to light after a 75-year-old businesswoman who visited the Starlight Dance Club in Wan Chai was confirmed as infected on November 19, sparking a race to track down contacts of infected patrons and staff.

Some of those in the cluster, including a 29-year-old man, had been to as many as five separate venues before the onset of symptoms.

Health officials identified a total of 28 dancing and singing venues linked to the cluster.

In a bid to contain the outbreak, the government required mandatory testing for the first time since the health crisis began in January. The testing orders were first issued to those who had visited the dance venues, then expanded to cover other emerging clusters.

The spike in Covid-19 cases also prompted Hong Kong and Singapore to postpone a quarantine-free air travel bubble – the world’s first such agreement – in late November, just a day before the first flight was due to take off.

Spread of the cases among dance clubs

Location of the clusters

What are the dance clubs like?

Hong Kong’s vast network of dance venues includes clubs, studios, restaurants, banquet halls and private establishments.

The dance clubs – not to be confused with nightclubs – operate as social venues where food and drinks are served, and cater largely to wealthy women. At Chinese restaurants and banquet halls, meanwhile, an afternoon mahjong session followed by a night of dancing and live music was a popular pastime before the outbreak.

Some clients would book out a restaurant to host social events, including private or group dancing and singing lessons.

Well-heeled, mostly female members of the community were said to spend huge sums of money on dance lessons, even illegally ferrying instructors into Hong Kong across the border from Shenzhen.

They would pay all associated expenses, including for entry fees to venues and meals. Some would even buy luxury gifts for their teachers, such as brand new iPhones, Rolex watches and designer clothing.

Less than two weeks after the first infection at Starlight in mid-November, new outbreaks tied to dance venues emerged at two housing estates and an elderly care facility.

The outbreak at Richland Gardens, a subsidised housing estate in Kowloon Bay, forced many residents to evacuate after design problems were found in the estate’s sewage system that could potentially facilitate the virus’ spread.

All residents in the D units of Block 6 were sent to quarantine, and more than 1,000 residents in three blocks had to undergo compulsory Covid-19 testing. A 69-year-old woman who lived in a D flat of Block 6 was found to have visited three dancing venues.

Residents of the fifth floor of Block 8 at Kwai Shing West Estate in Kwai Chung were also sent to quarantine after people who lived in separate flats there fell ill. While the outbreak was initially limited to the fifth floor – where a 77-year-old man who visited the Kam Lai Club in Mong Kok lived – it rapidly spread to different levels, prompting authorities to require mandatory testing for the whole block.

The cluster also spread to Ho Yuk Ching Willow Lodge, a care facility for the elderly in Tai Kok Tsui, after a 59-year-old caregiver there was confirmed to be infected on November 30. She lived in Tak Long Estate in Kai Tak, where some infected residents were also found to have visited the dance clubs.

So far, the outbreaks attributed to the dance cluster at the housing estates and the elderly care home account for 54 infections, and four fatalities, all of which were at Ho Yuk Ching.

Outbreaks at two major private hospitals accounting for a total of 14 cases were also believed to be linked to the dance cluster, but are not officially included in the total tally of 732.

Hong Kong’s intergenerational dancing community cuts across social class, with people from both lower-income and wealthy households falling ill after visiting the dance venues.

A total of 305 people – 122 men and 183 women, aged 19 to 89 – in the cluster went to at least one dance club either two days before onset of symptoms or during their incubation period.

Of those patients, 76 women were between 60 and 69 years old, representing 41.5 per cent of females in the cluster who went to the dancing and singing venues.

There was a double-digit difference between the average age of female and male patients at 16 of the 22 dance venues infected people visited.

For instance, at Starlight, only two female patients were in their 30s, while the other 19 were aged 55 or older. By contrast, two-thirds of the 24 male visitors to test positive were in their 20s and 30s.

But the ages were less skewed at Kam Lai Club, which had the most confirmed cases, with 92. There, the average age of both male and female visitors was 62 years old.

Separately, only male visitors tested positive at Chasse in Wan Chai. They were between the ages of 29 and 47.

Dr Joseph Tsang Kay-yan, an infectious disease specialist, said the super-spreading event in dance clubs created a sudden surge in cases, which increased the workload for contact tracers and piled pressure on isolation facilities.

He noted that some people were not willing to disclose that they were part of the cluster, making it difficult to conduct contact tracing.

“Due to privacy, there were missing gaps, which made it hard to link up and identify potential cases or close contacts. People could be spreading the virus in the community while authorities tracked them down,” he said.

Tsang pointed out that the dancers spanned all social classes, and spread the virus to their families and close contacts.

He added that their residences, particularly public housing estates with old drainage systems, could also be prone to spreading the virus to other flats, creating new chains of transmission.

“The super-spreader event created many chains of transmission in the community, which amplified the consequences,” he said.