ASHRAE continues to develop extensive publicly accessible resources on HVAC systems and Covid-19.  These include recommendations on design, operation and maintenance.  AHSRAE’s web page also links to guidance from other organizations.  If you are looking specifically for information on building operation during the pandemic, this ASHRAE Journal article might be helpful.  ASHRAE has also published “core recommendations” for reducing aerosol exposure.

ASHRAE Resources on Covid-19 and HVAC Systems