Valid reason to quit?

Would it be a valid reason to quit your job due to your health? I work as an afterschool counselor so I’m with kids a lot. I have a low immune system to begin with. They told me the first time I got sick that I’d get sick a lot the first 2 months or so. I’m already 5 months in and I’ve been getting sick at least once every month. I got the flu a week ago and already yesterday I started getting sick again. I don’t think this is very normal the fact I’m getting sick so often when before I wasn’t getting sick so much. I’m wondering if this would be a valid reason to quit a job?