Hello and welcome, any sort of infection let alone covid can cause a sudden downturn but not always permanently so, bacterial infection like a Urinary Tract Infection (UTI) are often quoted, however, viral infections like covid, no idea, that said long covid is a whole different ball game if that's what it turns into.
Had covid myself, not the best of times and I post on here as a carer, took me out of the game for some time.
All better now sat posting in the kitchen at home against all odds.
All here to listen. K