Standby to work everyday

I supposed to have holiday tomorrow. But the duty is amended again as many staffs sick leave. Thus, I need to go back to work tomorrow. It seemed that even the manager said that you will have holiday in a certain of day. It is never be true. It will be changed all the time. I hope that my colleagues will be getting well soon. By the way, I have received news that three staffs had dinner with me being sick right now. I am now becoming a high-risk person to be sick. I will try all my effort to fight.