Questions about herpes

My little brother was super sick the past couple of days, the dentist diagnosed him with thrush, but the ER today diagnosed him with “non sexually transmitted herpes”

So the thing is, he is sick like he has an infection. (Dizzy, nauseas, etc) and his gums are sore and bleeding but he has no sores on the outside of his mouth. It’s all internal. Yesterday on his way to the dentist he mouth started bleeding profusely and he thought his gums were dissolving, I made him pull over and drove him to the dentist, his breath was RANK.

Does this sound like an onset of herpes??

Also, how contagious is he? I have a 7 month old and two kids that adore him. My family is awful about keeping track of cups when there’s an event. Can he never kiss anyone again? How is it not sexually transmitted? It’s not cold sores so I’m confused.

Can anyone educate me??

*hes 21, but a virgin.