Feeling really anxious, could use some support :(

I wrote a post in the " General discussion" yesterday, saying that I started a new job few days ago as an administrative assistant in a primary school. I was supposed to take care of sick kids until their parents can pick them up. Obviously, it's my worst nightmare and I felt relieved after telling the truth to my employer who was very understanding and told me that she will find a solution.
BUT for some reason, I feel really anxious because tomorrow, I'll be alone in the office, so what if a kid get sick? And what if my employer didn't tell the teachers I wouldn't be able to take care of them? I feel trapped and I get anxious everytime a classroom door opens ... In addition to that, I feel guitly because I really do love kids but I just can't deal with them being sick. That's the first reason why I am feeling so bad right know. The second is I am obviously scared to catch a virus (I don't mind a cold, you know what type of virus I am talking about ... ). I wash my hands a lot etc the problem is I barely eat because of my anxiety. I know it's wrong because if I am weak, I can get sick a lot easier. But I just can't.

I wrote a lot, I'm sorry. I just feel bad and this website seems to be the only place where I can get help from someone who really understands ...

You know what time your work day ends. Try to focus on that. Say, "Even if a kid comes in the office sick today and I have to sit with them, by 3 pm (or whatever time it is) I will get to go home and I'll be safe. I'll almost certainly not get sick myself but if I do, I'll handle it." Put a timer on your fear. Even consider, "if I do have to sit with a sick kid tomorrow, will that matter a week from now? Even if it made me sick, a week from now I'd be better anyway like nothing ever happened."

Chances are nobody will come in sick to your office, and even greater chances are that you won't catch it even if they do. I wonder why they don't stay at the nurses office when sick? That's how my school always was.

Thank you, your reply helps a lot. I'll try to focus on the time my work day ends (4 pm) ...
Problem is they don't have a nursery. I live in France and we don't have nurses office in primary school. I wish we could because I wouldn't have to worry about that !