While recent research has explored the seasonality of COVID-19, it is the overlap of seasons and HVAC system operation that determines the indoor environment—where most viral propagation occurs, according to an article on the Consulting-Specifying Engineer website.
Research has linked air between 40 and 60 percent relative humidity (RH) with less-effective aerosol travel, shorter airborne and surface survival times, lower transmission rates and more effective patient lung repair functions.
However, hospitals in colder climates typically operate at lower RH levels (often 20 percent-30percent) during winter, in line with minimum requirements.
Most Northern Hemisphere cities have a window of opportunity before summer arrives to increase humidification to 40 percent.
Ventilation and Filtering for Infection Control 
ChristianaCare Opens Aston Campus Neighborhood Hospital
Stantec Breaks Ground on New Academic Medical Center in Miami
Building Senior Living for the Next Generation of Retirees
Managing Drain and Biofilm Risk