Just give symptomatic and supportive treatment. Nothing much to worry about. Will subside on its own in 5 - 7 days. Just beware of the symptoms of pneumonia. To prevent secondary bacterial infection, you can add oral Amoxyclav for 5 - 7 days.

Adenovirus just like common cold often causes self-limited respiratory, gastrointestinal, and conjunctival infections among healthy children. But for this virus, just ensure he is stable, feeding well and  has no evidence of respiratory distress. Give him adequate amount of fluids, along with an antibiotics to cover secondary bacterial infection.

Greetings need not to be worried you need to hydrate the child well , give the medicine that it