An invisible threat, germs can’t be easily avoided—especially if your day requires you to venture out of the house.

“Public places where a lot of people congregate, such as shopping malls, sports stadiums and restaurants, are likely to harbour bacteria and viruses that could give you a nasty gastrointestinal infection,” says Glen Armstrong, head of the Department of Microbiology & Infectious Diseases at the University of Calgary.

It’s the surface areas people frequently touch which are most likely to be rife with germs, while a warm and moist environment offers the perfect breeding ground. “Indoor areas, especially ones that are overheated, facilitate the spread,” says Armstrong.

Here are the top places germs hang out, and how to best protect yourself.