Hi
Forum rules prevent us diagnosing or trying to diagnose, but people might be happy to share their personal experiences.
It's fairly common for a period of illness to go along with a raised BG - I've had this and you'll find many other accounts on the forum. The body seems often to respond to illness by providing more glucose. Sometimes I'll see the BG rise a day or so before I start to feel off.
That said, the increase in your A1c result is comparatively small and could be entirely caused by the 5% acceptable error in the HbA1c test. A true A1c of 52/53 could give results of 50 or 55, admittedly at the opposite ends of the allowable range.