I've lost quite a bit over the winter, between stress (family member illness), my own bout with flu and a pesky thyroid condition, not being able to get in a long ride more than once a week, etc.
I'm trying to get in more overall conditioning at home, and avoiding too much riding in freezing temps. I don't mind the cold in terms of overall comfort, as long as I'm dressed appropriately. But it does seem to aggravate this respiratory bug.
On the one hand, my average speed over familiar routes is way down.
On the other hand, my top end is a bit better, especially hill climbs. I just don't have the stamina to sustain it over distance. I've set several personal bests on some climbs that had thwarted me for months. But then I need to loaf on the flats to recover.
Overall, can't really complain. It'll come back this spring.