For several of the pathogens we will discuss (such as Shigella, Staphylococcus aureus, and Norovirus), transmission from other humans through poor sanitary practices is an important risk factor. Surface transmission seems to be the major factor behind an outbreak of Norovirus that occurred among hikers on the Pacific Crest Trail. This outbreak was a bit unusual, as Norovirus outbreaks are more often associated with schools and cruise ships. However, in this case, a specific rest stop along the trail was implicated. You can read more about the work that was done to identify the source of transmission here and here.
