Crowd capacity for the Sydney Test between Australia and India starting on Thursday has been reduced to 25 per cent.

Questions were raised over the venue of the third Test after a coronavirus outbreak in New South Wales.

The clash will go ahead at the SCG, but on Monday it was announced the crowd capacity had been cut from 50 per cent to 25.

"In response to the public health situation in NSW, we are working closely with Venues NSW and NSW Health to put appropriate biosecurity measures in place for our staff, players, match officials, broadcasters and fans to ensure we play the third Test at the SCG safely," Cricket Australia (CA) interim chief executive Nick Hockley said.

"Reducing the capacity of the venue is crucial in achieving social distancing requirements, and we sincerely thank ticketholders for their patience, as we process refunds today, reconfigure the SCG seating plan to deliver these social distancing measures and go back on sale."

The four-Test series is locked at 1-1, with some doubts now over the venue for the final match – due to be held in Brisbane.

Meanwhile, Australia paceman James Pattinson has been ruled out of the Sydney Test due to bruised ribs suffered in a fall at home.