What the handling of the Chadstone coronavirus cluster reveals about Victoria’s contact tracing
By Ben KnightPosted Yesterday at 6:12am, updated Yesterday at 7:53pmSpace to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. 02:3302:33
On September 21, Daniel Andrews told Victorians: “This is not just a good day. It’s a great day.”
Many agreed. The sun was out, and for the second day running, the state’s new case number had dropped to single figures.
What Victorians didn’t know was that an outbreak that would derail their hopes of emerging from lockdown was beginning its spread.
The outbreak now exceeds 40 cases, spreading from Chadstone to Kilmore and onto the northern Victorian city of Shepparton.
An ABC analysis of the contact tracing effort has identified potential missed opportunities to stop the spread, and a massive change in approach from the beginning of the outbreak to the end.
Four-day delay in discovering link between cleaner and Butcher’s Club
Health authorities say the Chadstone outbreak began in Frankston, with a cleaner who was living with family members who were sick.
After attending The Butcher Club at Chadstone for work between September 21-23, she called the business on Thursday, September 24 to tell them she’d been told by police to stay home.
Two days later on Saturday, she tested positive to coronavirus.LIVE UPDATES: Read our blog for the latest news on the COVID-19 pandemic.
Contact tracers are trained to ask where people work, and are on particular alert for high-risk jobs like cleaning.
However, the cleaner did not tell contact tracers where she worked, so for four days The Butcher Club was not officially informed of the risk.
A staff member at the shop fell ill and returned a positive test on Monday, September 28.
Contact tracers only discovered the cleaner had worked at The Butcher Club while infectious after the staff member got sick and the shop shared their staffing information with DHHS.
Kilmore traveller unaware they had become linked to outbreak
Two days after the manager of The Butcher Club tested positive, the virus spread from there to Kilmore, when a person sharing a house with another Butcher Club employee drove into country Victoria for work.
The person stopped at a cafe for breakfast, infecting a staff member, and sparking a new cluster that has now grown to at least six cases.
The day before, the Department of Health and Human Services (DHHS) had listed The Butcher Club as a high risk location.
But for some reason, the person living with a Butcher Club employee didn’t get the message.
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‘Contacts of contacts’ approach phased in
The contact tracing and testing program in this outbreak has been markedly different from its beginnings in Chadstone to the current approach in Kilmore.
In Kilmore, the net has been cast far wider than usual. For the first time, everyone who was at the affected site has been told to isolate and get tested, along with their immediate close contacts.
To date, nearly 1,000 people in Kilmore have been tested, and nearly 400 are in isolation. The current number of cases is six.
DHHS says the Kilmore approach is being “phased in”, and is also now being used for new cases related to the Chadstone cluster.
Active COVID-19 cases in Victorian postcodes
+−LeafletActive cases0≥100Last updated: Tuesday Oct 13th 2020.
When asked on Tuesday why the approach taken in Kilmore was not adopted for the Chadstone outbreak, Chief Health Officer Brett Sutton said the scale of asymptomatic testing required at Chadstone would not have represented “value for money”.
“We’re talking about a number of shops in Chadstone where people hadn’t gone anywhere near any of those exposure sites, and so to open it up to every single asymptomatic person [to be tested] would not necessarily have been proportionate,” he said.
Professor Sutton also highlighted the “burden” for contacts of contacts to enter 14 days of quarantine.
“We’ve got hundreds of people isolating in Kilmore,” he said. “I think they accept that as a legitimate and proportionate measure to control that outbreak.”
Public health physician Nathan Grills, an associate professor at the University of Melbourne’s School of Population and Global Health, agreed it was important the number of people being asked to enter quarantine was proportionate to the outbreak in question.
“I think the risk with broadening quarantine or home isolation measures is that you scare people away from identifying as contacts, or even getting tested,” he said.
“If people know that identifying as having visited an area may mean severe restrictions — such as mandatory testing, arbitrary home isolation and additional restrictions on their family — then they may hesitate to self identify as at risk and avoid testing.”
Questions remain over why workplace link wasn’t picked up
University of New South Wales epidemiologist Mary-Louise McLaws, who is an adviser to the World Health Organization, said questions remained around why a contact tracing interview with the cleaner as a close contact did not reveal a link to the Butcher Club earlier.
Professor McLaws said the most recent version of Victoria’s contact tracing questionnaire she had seen included questions on a person’s occupation and employer and should have revealed the recent shifts at the Butcher Club.
“Importantly, she should have been interviewed as a close contact of her family members who are unwell and therefore a potential risk to her workplace,” she said.https://www.abc.net.au/res/sites/news-projects/covid-victoria-roadmap/1.2.3/?abcnewsembedheight=570
Professor McLaws also questioned Professor Sutton’s position that asymptomatic testing of everyone who had visited Chadstone would not represent “value for money”.
“What’s the value of having a third wave compared to hundreds of extra tests?” she asked.
“And yes, you might not find a lot of cases, but if the cleaner was infectious you might find others before they become a source of infection.”
Professor McLaws welcomed the handling of the Kilmore outbreak as a “good thing”, and not dissimilar to the approach taken in Tasmania to prevent a hospital outbreak in Burnie from overwhelming the regional town earlier this year.
“That sort of true ring-fencing style, where you ask everybody to go into quarantine or isolation regardless of whether or not they’re testing positive,” she said.
“This is highly precautionary, and it’s something that outbreak managers do when they believe that there’s a big risk of people being highly interconnected and therefore a rapid transmission.”
She said there were lessons to be learnt from the outbreak.
“This case of the cleaner reminds me that cases are part of the community and unless you do a thorough and deep contact tracing, people will escape inadvertently,” she said. “And if they’re highly infectious, they have the opportunity to cause more clusters.”