My Grandson Is Three Years Old And Was Sent Home

My grandson is three years old and was sent home today from daycare with a fever of 101 and he's coughing and his baby sister has the flu, so when he came home and took a nap he woke crying and looking very scared and shaking a little so after his mom calmed him down, 15 minutes later he was screaming and crying again and he was awake still and when she asked him what was wrong he said he didn't know, so could this be hallucinations?