“I think there are genuine structural issues about work,workforce,that make transmission more likely. They do the right thing. But they have some vulnerabilities in terms of where and how they are needing to work.”

There were 84 active cases in City of Casey on Monday,fewer than Wyndham,Brimbank or Melton.

Mobility data from Google and Facebook shows people living in Casey,the local government area that covers Hallam and Narre Warren,have been leaving home more often during Melbourne’s lockdown,on average,than other areas.

The stage-four lockdown,which targeted businesses,appeared to reverse that trend,said Melbourne University researcher Rohan Byrne,who is part of the team of scientists tracking the virus for the federal government.

But in the past fortnight,people in Casey have started leaving their homes again,he said. Most of that activity happened during weekdays,suggesting a strong link with work.

The data also shows when people in Casey do leave the house,they are more reliant than other areas on public transport.

University of NSW bio-statistician Dr Nicolas Rebuli said:"I’d consider both of these activities quite high risk – especially if they have high-risk occupations."

The Afghan community in Melbourne’s south-east is particularly vulnerable to the virus,as some of its members cannot read the health messages,community leader Bassir Qadiri said.

While the community has been complying with the stage four restrictions,Mr Qadiri has been translating public-health messages into Dari and calling members of the Afghan community,especially vulnerable elderly members of the community,to go through the information with them.

He confirmed he had heard of two Afghan families in Hallam who had fallen ill with COVID-19.

Southern Migrant and Refugee Centre chairman Brian Oates said that aged care and insecure work would most likely be driving transmissions.

"It does seem that aged care workers are the conduit for the coronavirus in many occasions. Aged care workers tend to be casual people who work in two or three different facilities at the same time in order to make ends meet,"Mr Oates said.

"People just have to work in several different areas because they can't get enough work in a single job as a casual worker. It's very disappointing and I think is one of the big lessons from this COVID situation. We need to pay more attention to insecure work."

The Agehas reported extensively on potential links between disadvantage,insecure work,and the spread of COVID-19.

Mobility data shows that on average more-advantaged areas of Melbourne reduced their mobility than less-advantaged areas during lockdown.

Workers in Casey were mostly employed in aged care,hospitals,supermarkets,takeaway food and childcare at the time of the 2016 Census.

Those industries are all considered essential and cannot be done from home,and have been identified as the most difficult workplaces to suppress the virus.

Responses show that 3.7 per cent of people in Hallam work in aged care,compared to 1.8 per cent of people in other Victorian suburbs. But fewer Hallam workers were employed in hospitals than the state average.