Australian Test captain Pat Cummins has been ruled out of the second Ashes Test against England starting in Adelaide later today.

The star fast bowler was exposed to COVID-19 in the 24 hours leading up to the match, with Cricket Australia forced to rule him out of the match.

"Cummins was dining in a restaurant last night and did not breach any biosecurity protocols. He isolated as soon as he became aware of the situation and has since had a PCR test which produced a negative result," a Cricket Australia statement read.

"SA Health has confirmed that Cummins is a close contact and will be required to isolate for seven days. As a consequence, Cummins is unavailable to play in the second Ashes Test match in Adelaide, starting today.

"We anticipate that he will be available to play in the third Ashes Test at the MCG in Melbourne."

With Cummins missing, he will be replaced by Michael Neser, who travelled with the squad to Adelaide, but missed the final pace bowling spot to Jhye Richardson, who is replacing the injured Josh Hazlewood.

It also means Cummins' vice-captain, Steve Smith, takes over as captain for the Test. It is the first time he was in charge of the national team since the Cape Town ball-tampering scandal in 2018.

Cricket Australia have announced Travis Head will play as the vice-captain.

According to Fox Sports, New South Wales bowler Harry Conway was also dining with Cummins at the restaurant, with the Adelaide Strikers player set to be unavailable for BBL duties ahead of his side's clash with the Sixers on Tuesday.

It is understood that Australian stars Mitchell Starc and Nathan Lyon were also in attendance at the same restaurant as Cummins and Conway, however the pair were situated outside, being deemed casual contacts and non-risks to play in the second Test.

It's understood Cummins will be fit to play for Boxing Day, however, Victorian rules require close contacts to isolate for a period of ten days, meaning he could only be released on Christmas Day.

The coronavirus pandemic has already caused a seismic shift to the summer of cricket, with the fifth Test forced out of Perth, with Hobart instead set to host that match.

A current outbreak in New South Wales and Victoria is picking up pace, and with state borders opening, cases are likely to increase across the country.