How do i explain to my daughter what it means to have atypical pneumonia?

She should relax: Atypical pneumonia is sometimes caused by a bacteria, and sometimes by a virus. It's a more benign type, and often caused by stress. What does her doctor say?

Simple is best: Just tell her she ended up catching some germs that decided to live in her lungs for a while. She will get better with treatment.You needn't be rattles by the "atypical" label, it has no bearing on success of treatment, its just part of medical lingo.