The majority of Victoria's 85 locally acquired coronavirus cases can be traced back to two "superspreaders" who attended sporting events while unknowingly infectious.
The first man, aged in his 60s, is a resident of the Ariele Apartments in Maribyrnong, which was visited by a COVID-infected removalist crew from NSW on July 9.
The man did not know he was infected with the Delta variant when a day later he went for a drink with a friend at the Young and Jacksons pub in Melbourne's CBD, before heading to the Geelong-Carlton Match at the MCG.
Nine people seated in the MCC Members Reserve and five of their close contacts have since tested positive for COVID-19, as well as seven people linked to Young and Jacksons.
Among those to contract the virus at the MCG was a man in his 30s, who 30 hours later attended a Euro 2020 championship viewing party at the Crafty Squire in Melbourne's CBD.
He left the event and headed to Trinity Grammar in Kew, where he works as a teacher.
The next day, he had dinner at Ms Frankie in Cremorne with 12 friends before heading to the Australia-France rugby union test match at AAMI Park.
The man also did not know he was infected and was asymptomatic at the time.
Nineteen staff and patrons of Ms Frankie, nine students and staff at Trinity Grammar, three people at AAMI Park and one person at the Crafty Squire have since tested positive for COVID-19, sparking their own chains of transmission.
Premier Daniel Andrews said the two "superspreader events" had proved the need for a statewide lockdown.
"The speed with which this has moved through the Victorian community confirms that we did the right thing to lockdown and it sadly confirmed that we need more time," he told reporters on Tuesday.
The state's stay-home-orders are now in place until at least 11:59pm on July 27.
Victoria's Chief Health Officer Brett Sutton said thousands of close contacts, who are considered most at risk of contracting COVID-19, are scattered across the state because of the sporting events.
"This outbreak has touched the whole state, and that was in a way that the Delta and Kappa outbreaks did not back in May and June," he told reporters.
"Much of that is due to the super spreading events early on in this outbreak that took place in the MCC members' reserve for the Geelong-Carlton game.
"It is something that brings Victorians from far and wide and back home far and wide across Victoria. Those impacts are rippling across the state."
Professor Sutton said people infected with the Delta variant appeared to be passing the virus on to others less than 24 hours after being exposed themselves.
"That tells us why we need to be across each and every infectious case," he said.
There are more than 18,000 close contacts self-isolating and more than 300 exposure sites associated with the current outbreaks.