Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
This usually requires planned assessment rather than emergency care.
Call emergency services for severe breathing difficulty, a seizure, sudden major vision loss, severe confusion, collapse, or difficulty waking.
These symptoms need immediate care, whatever the cause.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek prompt, same-day medical advice if you have weakened immunity and develop:
New blurred vision, floaters, blind spots, or eye pain
Ongoing fever, diarrhoea, abdominal pain, or pain when swallowing
Increasing shortness of breath
New weakness, poor balance, or changes in thinking
A newborn should be assessed promptly for poor feeding, unusual sleepiness, jaundice, a widespread spotted rash, breathing problems, or possible seizures.
And for anyone, someone who:
has a fever with a stiff neck, a rash that does not fade under pressure, or severe headache
has a wound that is hot, spreading red, or leaking pus
3
Does any of this apply?
Book an appointment
Arrange a routine appointment for persistent fever, swollen glands, or unusual tiredness that is not improving, particularly if your immune system is weakened.
The article also says
Contact your pregnancy or maternity team if you are pregnant and have a possible CMV-like illness, concerning exposure, or abnormal blood or ultrasound results.
Every sign above is quoted from the sofidex article on Cytomegalovirus (CMV) infection. If you are not sure, err upward — it is always reasonable to be checked.