[NautiNurse]

Maybe it’s in the water, and the city/state is spreading it.

Your theory is reasonable. A multitude of possible transmission means exist in the big city. Garbage chute handles, stairwell handles, elevator buttons, shared laundry facilities, etc., and those means are solely while sheltering-in-home.

[StolarStorm]

I’m betting a lot of older apartment building have common air ducting.