Final answer:
The transfer of pathogens through contaminated instruments or surfaces is known as cross-contamination, which is particularly common in crowded urban environments through fomites like doorknobs and towels.
Step-by-step explanation:
When contaminated instruments or surfaces transfer pathogens, it is referred to as cross-contamination. This often occurs in densely populated urban settings where the spread of infection can be facilitated by touch, when either infected individuals make contact with others or when they come into contact with objects that are then touched by non-infected individuals. Objects like doorknobs, toys, or towels that can harbor microbes and aid in disease transmission are known as fomites. To handle these risks, certain infection control practices are necessary, but not all require sterilization; the method used depends on the level of cleanliness needed and the resistance of potential pathogens to treatment.