"Contaminated surfaces" refers to objects or areas that have harmful substances, such as germs or chemicals, on them, which can be passed on to people who come into contact with them. Full definition
The infectious agents can be transmitted through the air, by direct contact with an infected dog (such as touching noses or barking through a fence) or by contact with contaminated surfaces. (Windmillvet.com)
Further analysis suggests that the infection may be transmitted within hospitals via contaminated surfaces and through airborne transmission. (sciencedaily.com)
It's found on contaminated surfaces, in soil, or on food or water that has been contaminated with feces (poop) from infected humans or animals. (pethealthnetwork.com)