When my mother was in hospital a year ago, and being shuffled between Hospital and Rehab, she tested positive, and then tested negative soon after. Although she was not considered to have had Covid, after the first two weeks in hospital she came home with a chest infection, which she passed onto most of our small family group. This was a persistent cough so may well have been Covid, We'll never know.
The point is, my personal experience shows just how confusing the picture was a year ago. Testing was hardly established. People got viruses, but there was no effective collection of data at that time, so comparisons now are quite meaningless.
