What action should i take if i suspect someone at my workplace has the virus of has been exposed?

You are not expected, and should not try, to diagnose workers.

However, you have a work health and safety duty to minimise the risk of workers and others in the workplace being exposed to COVID-19 so far as reasonably practicable. 

If you reasonably suspect someone has the virus, or has been exposed, this creates a health risk at your workplace, and you will need to follow the steps below. Do not wait until confirmation that a worker has COVID-19. You must act promptly to take reasonable steps to manage the risks.  

This information is provided to assist you in the workplace. However, you must always follow the advice of your state and territory public health unit and WHS regulator, even if it is different to this guidance.