Can casuals call in sick?

I’m from Australia so not sure what the rules are for calling in sick as a casual. My workplace has recently had a lot of employees leave due to bad workplace environment with horrible shift planning, and a manager who frequently screams at employees. Now we are really short staffed and I’ve got the flu pretty bad and stomach bug, I tried calling in and they say they need me as their short staffed for tomorrow however, I can barley get out of bed as I’ve become really ill. Am I allowed to tell them I can’t come tomorrow, as I can’t imagine working retail tomorrow like this spreading my virus around to everyone.

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