South Australian senator Rex Patrick has become the fourth federal politician to test positive for coronavirus.
The crossbencher is in self-isolation at home after coming into contact with Liberal senator Andrew Bragg, who also has the virus.
"SA Health has advised me that, despite being asymptomatic, my COVID-19 test has returned positive," Senator Patrick tweeted on Monday.
"I have assisted them with comprehensive contact tracing and they'll call anyone considered at risk."
Senator Patrick sat next to Senator Bragg during a Senate committee hearing two weeks ago.
"Had the testing criteria been looser, he would have found out much sooner and I would have found out much sooner," Senator Patrick told the ABC.
"I would have self-isolated."
Senator Patrick, Senator Bragg, Nationals senator Susan McDonald and Home Affairs Minister Peter Dutton have all contracted the disease.
Senator Patrick said health authorities told him people who had spent 20 minutes within a metre of him or two hours in the same room should get advice.
"It can be caught by anyone from a senator to a janitor," he said.
