"Strict hygiene" means following very careful and thorough cleaning and personal care practices to keep yourself and your surroundings clean and free from germs or dirt. Full definition
The environment must be clean and sterile with strict hygiene standards typical of most medical facilities. (payscale.com)
Perhaps because of his nearly fatal illness as a teenager, he feared germs and practiced very strict hygiene, likely a barrier to the development of interpersonal relationships. (thenextweb.com)
There is no medical intervention that prevents the spread of the virus — it's all about strict hygiene efforts. (travelinsurancereview.net)