Australia has received a stark coronavirus reminder with South Australia preparing to enter the nation's harshest lockdown for six days to crush Adelaide's cluster.
Schools and almost all industries will be closed from midnight on Wednesday, while weddings, funerals and outside exercise are all set to be banned.
Takeaway food outlets will be shut along with pubs, cafes and food courts, while supermarkets and a handful of essential services will remain open.
"We are going hard and we are going early," SA Premier Steven Marshall told reporters.
The Adelaide cluster has risen to 22 cases, sparking the initial lockdown which will be followed by eight days of further restrictions.
South Australia has asked for an additional 45 Australian Defence Force troops to join the 100 already on the ground.
All hotel quarantine workers around Australia will now be tested weekly.
The Adelaide cluster and Melbourne's deadly outbreak both spread after the virus escaped hotel isolation regimes.
"That is our major risk now of reintroduction of COVID-19 into Australia, as we have seen in Adelaide over recent days," Acting Chief Medical Officer Paul Kelly told reporters in Canberra.
But Professor Kelly is confident South Australia will get on top of the latest infections.
"It is hard and fast," he said.
"South Australia has made the decision on the basis of the information that they have at hand.
"They know their system, they know their people, that is the decision they have made and we back them."
Senior federal cabinet minister Simon Birmingham also supports the state government's hardline approach.
"Yes it seems hard and tough right now, but if it avoids many months of pain down the track then it will be a week or two of difficulty that is worthwhile," the SA Liberal told Sky News.
Senator Birmingham said the strategy was to eliminate the cluster and community transmission of the disease more broadly.
A raft of border closures came before the lockdown announcement but were soon rendered meaningless with South Australians banned from regional and interstate travel.
The Adelaide cluster also prompted doctors to urge a cautious approach on returning to the workplace in other parts of the country.
Australian Medical Association president Omar Khorshid said it was too soon for a mass return to workplaces and public transport.
"The only way to keep these numbers low is to continue to follow the habits that have proven so effective in getting Australia to such an enviable position," he said.
Dr Khorshid said workplaces were one of the main places where coronavirus spreads.
"Working from home minimises the possibility of workplace transmission, reduces the geographic spread of the virus and makes our public transport systems safer," he said.
Victoria has now notched 19 days without a new coronavirus case.
ACT has recorded a rare infection, with a diplomat in quarantine testing positive for the disease.