Make it safe to speak up
Tell every food handler which symptoms to report, and that they will not be pushed to work with them.
A new starter hears on day one: if you've been vomiting, call before your shift, and nobody will give you a hard time.
A casual loses shifts after calling in sick once, so next time they come in and tell nobody.
Report jaundice, diarrhoea, vomiting, fever, sore throat with fever, visibly infected skin lesions, and discharge from the ear, eye or nose. Under Australian law, food handlers must report symptoms to their supervisor, and tell them if they think they have contaminated food.