If the place brushes your teeth close to the bathroom, then it's the same as brushing your teeth with what's in the bathroom.
one of the many ways a germ attaches to a toothbrush is through sprinkling of water and germs that fly through the air.
Not just that. By brushing your teeth, you can remove germs or blood and saliva containing viruses. If you do not clean the toothbrush properly, then you will likely re-enter the germs and virus into your mouth and body 