My 2 Year Old Was Diagnosed With Herpangina. His Fever

My 2 year old was diagnosed with herpangina. His fever is gone already but still has sores in his mouth that prevent him from eating and hardly drinks water. But he recently developed very bad breath and keeps getting stronger. Until now he never had bad breath even when waking up in the morning until he got this herpangina. Is it normal to develop bad breath? I'm really concern. He has 5 days with this already.