Melbourne had a mutated virus ..... and beat it
Turns out one of the virus variants circulating in Vic was a precursor to the UK variant and was more infectious than the original one (but possibly less so than the UK variant):
"A mutant strain of the coronavirus which scientists believe was a precursor to the highly infectious British variant escaped hotel quarantine in Victoria in June during the state's second wave but the public was not told about it at the time.
Professor Damian Purcell, head of the molecular virology laboratory at the Doherty Institute for Infection and Immunity in Melbourne, said the new strain infected at least 37 people in Victoria before being brought under control by Victoria's lockdown
The information had not been released until now, he said, because “we did not want to spook people that we had a real problem with mutants here”.
“We expect to see them. They are going to keep coming,” Professor Purcell said."
https://www.theage.com.au/national/public-kept-in-dark-after-mutant-virus-seen-in-victoria-s-second-wave-20210107-p56sa3.html
The good news is that isolation, masks and hygiene were effective against it.