Bob
I know this bunch and they are very knowledgeable. Download this advisory - it's aimed at how to manage building services during COVID19 but is very interesting about the virus itself:
https://www.rehva.eu/fileadmin/user_...3-17_final.pdf
Basically ventilate as much as you can and close the bog lid is the advice for home owners. I'm getting out into the fresh air as much as I can in my back garden
I think you're doing everything that you can do to keep safe based on what we know.
PS It's still cold - hence everyone else's windows being closed if they're heating their houses