The NSW government had given the green light for Cricket Australia (CA) and Venues NSW to host a half-full crowd of approximately 20,000 for each day of the third Test.

However, Sydney's COVID-19 outbreak means that number has been trimmed to approximately 10,000.

The Australian Medical Association has led calls for Test to be played without spectators because of the risk it could be a virus super-spreading event.

Acting NSW Premier John Barilaro insisted on Monday that the Test could be staged safely, yet urged cricket fans in regional NSW to reconsider attending the game because of the risk "they could take it (coronavirus) back to a regional area".

"The capacity of 25 per cent is where we're starting. Our plan is scalable," Venues NSW chief executive Kerrie Mather told reporters.

"Tickets will initially be available based on that capacity.

"If there was the opportunity - in what is a very fluid environment, and an improving situation - to host more, we could certainly host more."

NSW Health will ultimately determine whether any additional fans are allowed through the gates during the clash between Australia and India.

Sydney's number of coronavirus cases will dictate what is possible but predicted showers, which health officials are concerned could affect social distancing, are also part of the puzzle.

"With the sort of crowd that we're talking about, there will be plenty of space," Mather said.

"We strongly encourage people to actually bring masks with them. If they don't have masks, we will be handing them out.

"When people are moving around the venue, they should wear a mask at all times."

The nation's Chief Medical Officer Paul Kelly has had "several discussions" with NSW counterpart Kerry Chant about the SCG Test.

"I've shared my insights into how that sort of event works. She's taken that on board," Kelly said.

"There are a couple of things that need to be addressed and I am confident they are addressing them."

Chant suggested there had been "extensive planning to manage those mingling points (at the ground) because that's really what we're concerned about".

Ticket refunds will be processed from Monday as CA and Venues NSW hastily reconfigure the iconic ground's socially-distant seating.

"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," CA's chief executive Nick Hockley said.

The NSW government reported zero new cases of COVID-19 local transmission on Monday.

However, Barilaro cautioned that two new cases will be part of Tuesday's numbers and that testing numbers are "far too low".

Australian Associated Press