The first change of human behavior that comes to mind to decrease exposure to microbes is washing hands often and sanitizing often. When I had in person classes I would get sick often because I would not wash my hands before eating, and I would eat in class a lot so all the germs and filth on my bike handlebars, backpack and phone would go straight into my mouth. Another behavior could be properly freezing and cooking foods to ensure all the bacteria are dead. Antibiotics can also cause decreased exposure to good and bad microbes but antibiotics tend to do more permanent harm and is not worth the temporary fix of killing off the bad microbes. Regularly cleaning the house especially the kitchen and bathroom areas can also decrease exposure to microbes. One last thing that I can think of is regularly bathing.
