The man, aged in his 30s, contracted the virus at the Geelong-Carlton game at the MCG on July 10.

He was seated in the MCC Members’ Reserve near a man in his 60s who lives at the Ariele Apartments in Maribyrnong, which had been visited by a COVID-infected removalist crew from NSW a day earlier.

About 30 hours later the younger man was at a viewing party at the Crafty Squire in Melbourne’s CBD, watching Italy beat England in a penalty shootout to win the Euro 2020 championship.

At about 8am on July 12, 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 had no idea he was infected with the Delta variant and was not presenting with symptoms at the time.

Twelve staff and patrons of Ms Frankie, six 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.

Victoria’s Chief Health Officer Brett Sutton said it proved the speed and ease with which the Delta variant spreads.

“It is absolutely an example of how quickly this variant is moving and the short time we’re seeing between exposure and then being infectious,” he told reporters on Monday.

“Last year we would not have seen any circumstances where someone who had been exposed was transmitting to someone else a day and a half later.”

COVID-19 Commander Jeroen Weimar said the latest outbreak was being fuelled by people under 40 with busy social lives.

The majority of people in this group remain ineligible for a COVID-19 vaccine.

“It’s a younger group of people that are really socially active, they go out and do loads and loads of stuff in quite constrained places,” he told reporters during a briefing on Monday.

“You can see that kind of activation where you’re going to Ms Frankie and then people who are at Ms Frankie are going on to other pubs and clubs and suddenly you’ve got almost 300 exposure sites for a very small number of cases.”

There are more than 15,800 close contacts self-isolating and more than 300 exposure sites associated with the current outbreaks.

The man in his 60s is believed to have infected a dozen people at the MCG, including his friend, who went on to spark outbreaks at Bacchus Marsh Grammar and Barwon Heads Primary School.

The duo attended Young and Jacksons pub in the CBD prior to the match, where seven people also tested positive for COVID-19.

Weimar said the state’s contact tracers were moving faster than ever before to stamp out the outbreak and have been aided by the lockdown, which came into effect at 11:59pm on July 15.

Premier Daniel Andrews confirmed the lockdown will be extended beyond 11:59pm on Tuesday, saying there were still “far too many” cases of community transmission to ease restrictions after five days.

“It would be perhaps a few days of sunshine and then there would be a very high chance we’d be back to lockdown again. That’s what I’m trying to avoid,” he told reporters.

Victoria’s public health team and senior government ministers will make the final call on the length of the extension by Tuesday morning.

Monday’s testing figures and results, as well as any new exposure sites and mystery cases, will guide their decision.

But he conceded there were still “far too many” cases of community transmission for the lockdown to lift as planned at 11:59pm on Tuesday.