The "Four F's of Infectious Disease":

Fingers - improper handwashing or failure to wash hands regularly is one of the most commonly avoidable ways to prevent the spread of infectious disease.

Fomites - any inanimate object a microbe can inhabit on a transient basis that can come in contact with a person, such as table and countertops, cups, dishes, towels, sponges, improperly sterilized laboratory or surgical equipment, gloves, doorknobs, drinking fountains or toilet seats.

"Flies" - a general term describing arthropod vectors of disease.  Diseases are spread either mechanically as microbes are picked up on the body surface and carried elsewhere or biologically when the arthropod takes a blood meal from an infected reservoir, then spreads the pathogen to new hosts when it takes new blood meals.

Feces - human and animal wastes harbor large microbial populations, many of which could be pathogenic or act as opportunistic pathogens when spread to food and water owing to improper sanitary techniques or contamination of water supplies caused by flooding or breaks in sewer lines.