 readily support microbial growth and can become secondary reservoirs of infection, though species are mostly those that threaten "at risk" groups.Pathogens (potentially infectious bacteria, viruses etc.—colloquially called "germs") are constantly shed from these sources via mucous membranes, feces, vomit, skin scales, etc.Thus, when circumstances combine, people are exposed, either directly or via food or water, and can develop an infection.