But what happens if one lands on your food? Do you have to throw it out?
In an article published on The Conversation, Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of Sydney, explains the health risks.
While there are hundreds of different fly species in Australia, the Musca domestica (aka the housefly) is the most common.
"When it comes to passing on pathogens, it’s not necessarily the fly itself but where it’s come from that matters,” said Webb. "Flies don’t just visit freshly made sandwiches. They spend far more of their time in rotting animal and plant waste. Among this waste can be a range of pathogens and parasites."
Flies don’t have teeth. Instead of chewing, they vomit digestive fluids to dissolve food before sucking it up.
Because of the time it takes a fly to eat, Webb says, "A single touchdown is unlikely to trigger a chain reaction leading to illness for the average healthy person."
Instead, flies that go unnoticed are more of a concern.
“Flies that land out of sight and wander about for a few minutes vomiting and pooping on your food or food preparation area are more of a concern,” said Webb.
“The more time passes, the greater the chance of pathogens left behind by the flies growing and multiplying on our food. That’s when health risks increase.”