Don't use evaporative humidifiers(the motorized wet towel). I don't know if it actually cause legionellosis, but it's not very sanitary, and the sanitizing additives for those are known to be actually harmful.

Use boiling type humidifiers (basically just electric tea kettles).

Water evaporates alomost completely and is changed daily (I rinse both container and disks in the tub with high-pressure mode from showerhead), so I don’t think any contamination is likely.

Been doing this for years.