What's wrong with her?
She has a sore throat.
What's wrong with her?
She has (terrible) toothache.
What's wrong with him?
He has a headache.
What should we do to avoid this problem?
Wash your hands more, wear a face mask when going out, do more exercise, drink more orange juice....
What's wrong with him?
He has flu.
What's wrong with her?
She has an allergy.