For what it's worth, my sister developed polymyalgia rheumatica immediately after a bout with a nasty flu. She and I both had the flu, but I got over it without incident. I remember her asking me if I had all the horrible aches and pains that she did, which I didn't. Her PMR lasted almost exactly two years, and then went away as mysteriously as is came.

https://en.wikipedia.org/wiki/Polymyalgia_rheumatica

"Studies are inconclusive, however several somewhat common viruses were identified as possible triggers for PMR.[8] The viruses thought to be involved include the adenovirus, which causes respiratory infections; the human parvovirus B19, an infection that affects children; and the human parainfluenza virus."