Cricket Australia (CA) chief Nick Hockley has tested positive for COVID-19 but has had no direct contact with the Ashes squad, the governing body said on Monday.

Australia batsman Travis Head tested positive last week and will miss the fourth test starting in Sydney on Wednesday, while England head coach Chris Silverwood tested positive on Sunday while isolating in Melbourne.

"After experiencing mild symptoms, I immediately got a PCR test which has since returned a positive result," Hockley, who is "fully vaccinated", said in a CA statement released to Australian media.

"I am isolating at home with my family, who have returned negative results."

The fourth Ashes test will take place at the Sydney Cricket Ground from Jan. 5. Australia hold an unassailable 3-0 lead in the five-match series.