Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency care for severe breathing difficulty, seizure, sudden confusion, fainting, or rapidly worsening illness.
Contact a clinician promptly for new vision changes, ongoing fever, worsening diarrhea, pain with swallowing, jaundice, unusual bruising, or reduced feeding in an infant.
Routine follow-up depends on the setting.
A healthy person recovering from mild CMV may only need review if symptoms persist or worsen.
Depending on the child's findings, follow-up may also include eye examinations, developmental screening, physical or speech therapy, neurology care, and early-intervention services.
Families should keep these appointments even if the child seems well.
The article also says
A person with reduced immune function should follow the monitoring plan from their transplant, cancer, HIV, or infectious disease team.
Keeping scheduled blood tests and reporting new symptoms early can help identify CMV before major organ injury develops.
Children with congenital CMV need repeated hearing checks because hearing loss may appear or progress after the newborn period.
Every sign above is quoted from the sofidex article on CMV. If you are not sure, err upward — it is always reasonable to be checked.