you can reasonably suspect whether you have them or not when you simply trace your steps backwards for a week, have you been to a high risk countries in the list of 44 publish by the government? Are you starting to feel fatigue? Is your throat not feeling usual? simple steps like that can slowly narrow it down to whether you are a suspect or not.
however your team manager will laugh it off and say until I see you in a stretcher, hauled to the nearest hospital, I do not think it is anything to worry about, in that case, I think you need to slap them with the law and contact the NSW health department.
Don't let your employer bully you into not taking this seriously through scare tactics.
And yes such is the arrogance of the human species.