QUT sociologist and education expert Naomi Barnes said that was because the virus got into a school at the start of the cluster,and children moved through the community differently to adults.

“If an adult gets infected,they will usually go to a few places in their ordinary activities,and only a few of those,like a pub,might have the potential to spread the virus around,” Dr Barnes said.

“But school kids spend their days going from mass gathering to mass gathering – they go to school,where they’ll be in classrooms and even assemblies,then after school they go to a shopping centre or something like sports,which brings them into contact with more people.”

Dr Barnes,who is not an epidemiologist but who has done extensive work on how children move through the community,said understanding how children behaved differently to adults was the key to getting a handle on the current outbreak.

“When you understand the story of how this virus has spread,it makes it a lot more clear why it has been so severe this time around,” she said.

In addition to differences in movement,there is also the issue of transmissibility in young people of the Delta variant.

It was initially thought that COVID-19,unlike many other viruses,did not spread well in children and did not affect them badly.

UQ virologist Ian Mackay said Delta appeared to shift the needle back towards a more standard transmission model,where children were a major spreading risk.

“There’s a lot of congregation going on with children at these schools,and that makes the potential for spread much more risky than we would otherwise see if it were just one infectious person at a shopping centre,” Professor Mackay said.

“In my opinion,kids were always being affected[by COVID-19],we just didn’t see it because we didn’t have many cases.

“What we’ve seen this time is Delta occur in a school and take off,and that’s completely biologically plausible,and even expected.”

Masks were made mandatory in high schools and for primary school teachers and staff this week.

Children under 12 are not required to wear masks unless they are in year 7,even though they comprise at least 19 of the 63 cases linked to the Indooroopilly cluster.

“I’m sure as we come out of the lockdown,hopefully on Sunday,there will be further instructions about masks going forward,” Education Minister Grace Grace said.

“But,as we found,they are a very good way to stop the spread of COVID-19,and it will be up to the Chief Health Officer to advise about where we go.

“There may be some change,but at this stage,primary school students aren’t required to wear masks if they’re back at school.”