It is possible, but not likely for them to make humans sick. If a fruit fly happens to be carrying an airborne pathogen, such as a virus or bacteria, then it’s possible that the fruit fly could infect you. Fruit flies are generally not picky about their food and will eat whatever is in front of them without discriminating between meat and rotting garbage. As long as the host isn’t contaminated with any kind of nasty bug from its recent contact with people or animals, pests like flies and roaches can help keep environments cleaner than what we typically find in our homes and restaurants. This might actually be true since fruit flies clean up by eating bacteria-laden carcasses left around by other animals — including those other animals living.