Parties held for last weekend’s Grand Final of the Australian Rules season are being largely blamed for a 50% jump of Covid-19 cases in Victoria.

The state’s capital Melbourne traditionally holds the annual event, but two teams from the city travelled to the west coast city of Perth to play due to a lockdown.

Contact tracers found a third of Victoria’s 1,438 new infections reported on Thursday had broken pandemic rules by attending social gatherings on the Friday public holiday and on game day, officials said.

Jeroen Weimar, commander of Victoria’s Covid-19 response, said time would tell whether the infection jump was “one big rogue day” or part of a grave new trend.

He said: “Today highlights the consequence of hundreds of people dropping their guards, dropping their guard for very understandable reasons and we’re all fed up with (the lockdown).

“But this is a direct consequence of hundreds of decisions made on Friday and Saturday last week and the question now is how we manage this going forward.”

Melbourne’s lockdown is set to end on October 26 when 70% of the state’s population aged 16 and older is expected to be fully vaccinated.

Australia’s second-most populous city will overtake Buenos Aires next week as the city that has endured the longest lockdown in the world, Melbourne’s Herald-Sun newspaper has reported.

Stay-at-home orders in Argentina’s capital lasted 245 days.