Humidifier sales

According to a Yale study, UV, temperature, and humidity all affect the spread of Covid, with humidity having the most effect.

"In total, Chen and the members of his research team determined 17.5% of the virus’ reproductive number was attributable to meteorological factors. Specifically, they found that temperature accounted for 3.73%, humidity accounted for 9.35%, and UV radiation for 4.44%.

The fractions attributable to meteorological factors generally were higher in northern counties than in southern counties, meaning the people living in regions such as New England may need to be especially vigilant about the increased transmissibility of SARS-CoV-2 in winter, when cold and dry weather and low levels of UV radiation offer favorable conditions for COVID-19 spread, the researchers said."

https://news.yale.edu/2021/06/14/heat-humidity-and-uv-rays-linked-covid-19-spread-ysph-finds

Care must be taken in choosing and maintaining a humidifier that the unit doesn't provide a breeding ground for other organisms, e.g., Legionnaire's disease.

https://licross.com/home-humidifiers-legionaires-disease/

And if the humidity is not managed well, there can be other issues with the dwelling including mold as well as structural damage due to condensation exacerbated by the cold outdoor temperatures. Approach with caution.

A lot cheaper and more effective is UVC light...

Although I do recommend keeping your environment at 35% - 65% RH with 50% being ideal for comfort level...