South Australia has imposed travel restrictions on people entering from  Victoria as authorities race to track down hundreds of AFL fans who may potentially have been exposed to COVID-19.

People who visited potential high-risk COVID infection sites in Melbourne have been banned from entering South Australia after Melbourne man tested positive on Tuesday.

Health authorities are working with the AFL to track down hundreds of fans who attended the clash between Richmond and Geelong last Friday and then travelled on the same train as the infected Wollert man.

The man in his 30s tested positive for the virus just days after leaving hotel quarantine in South Australia.

Genomic testing supports the hypothesis that the man acquired COVID-19 in hotel quarantine in South Australia, according to Victoria’s Department of Health and Human Services.

SA Police Commissioner Grant Stevens told reporters on Wednesday he had signed a direction banning anyone who visited the sites from travelling into South Australia.

He said anyone who is already in South Australia and who visited the at-risk sites would be ordered to quarantine for 14 days and get tested.

Earlier in the day it was revealed the man had travelled to some of the city’s busiest train stations while infectious with COVID-19.

Victorian Health Minister Martin Foley stressed that anyone on the Friday night train services – identified as Tier Two exposure sites – must get tested and isolate until they receive a negative result.

Those were the 5.28pm from Craigieburn to Southern Cross and the 10.20pm from Flinders Street to Craigieburn.

“This advice applies to anyone in any carriage,” Mr Foley said.

“Given that it was the aftermath of the Richmond-Geelong game we are working with the AFL to get messages through all of their clubs and the data … get that material out to what we would expect to be many hundreds of people on that train.”

He also urged anyone who is eligible to get a vaccine to get vaccinated as soon as possible and reiterated the importance of following COVID safe measures. 

“We’re at a really critical stage here. The next day or two will be fundamental to getting this under control,” he said.

Health authorities confirmed no new cases of coronavirus had been recorded in the state overnight, but urged everyone to remain vigilant.

Before genomic results had been confirmed, Mr Foley said authorities would not put “all of their eggs in the genomic testing basket” by assuming the virus was acquired in hotel quarantine.

He said while it was “improbable” that the man acquired COVID-19 on his flight from Adelaide to Melbourne on May 4, he urged anyone who was on that JQ771 flight to get tested immediately.

“We want to chase every rabbit down every burrow and make sure that we leave nothing to chance here”, he said.

“Some of them, from the data that we’ve got from the national incident centre … would have moved on to other jurisdictions, but we look forward to all of those people getting tested and ruling themselves out as possible sources of acquisition,” he said.

The man flew into Adelaide from India via the Maldives and Singapore on April 19 before Australia’s flight ban began.

He has been listed as an interstate acquired case, was the only infection in Wednesday’s health department update.

It means Victoria has gone 75 days without a local case.

Tweet from @VicGovDH

A flurry of contact tracing has been underway, with ‘Tier 1’, ‘Tier 2’ and ‘Tier 3’ exposure sites listed, each with different isolation rules.

Anyone who had attended a ‘Tier 1’ venue was advised to immediately get tested and isolate for 14 days.

Those who had been in Tier 2 sites were told to get tested and isolate only until a negative test result is received, while ‘Tier 3’ must monitor for symptoms.

The full list of exposure sites is available here. 

The full list of testing sites is available here. 

It is expected that Victorians could return to tighter COVID-19 restrictions if evidence emerges that the man infected others in the community.

Mr Foley has earlier expressed disappointment the federal budget did not appear to provide any funding for the quarantine facility that Victoria wants built north of Melbourne.

COVID-19 response commander Jeroen Weimar has warned against complacency after it became evident that not everyone who attended a tier one exposure site had checked in using the QR code.

The owner of the Curry Vault Indian restaurant in Melbourne’s CBD thought there were 30 to 40 people at his restaurant on Friday night – but did not have details for all of them. 

“Based on information provided, we think there are likely to be more people in that restaurant than are on the QR code system at the moment. But we don’t know who they are,” Mr Weimar said.

“That’s why it’s so important that we all maintain the basic behaviours.

“Wear a mask in public transport and in taxis and when you can’t isolate, use the QR system wherever you go.”

South Australian authorities are examining whether the positive case contracted the virus before arrival and had an unusually long incubation period, or caught it from a person with the virus in a neighbouring hotel room.

All three of his household contacts have already returned negative test results, which Professor Sutton described as an “early encouraging sign”. 

-with agencies