In other words, all flies pose a threat. House flies, fruit flies, and cluster flies are examples of species that essentially transfer and spread bacteria and disease. They can spread infections wherever they land by snatching them up from locations like waste bags. Cholera, dysentery, and typhoid are a few diseases conveyed by flying insects, depending on the species.

Flies are drawn into homes by air currents, food preparation, and disposal. Flies may smell the smell of food inside or outside from trash cans. Certain flies can spawn in drains and trash cans, which can lead to populations growing inside of structures. Flies are drawn to warm buildings on cool days, whereas they may also be drawn to cool buildings on hot days. Flies may bring bacteria into the home since they often breed outdoors in dung, trash, and the carcasses of dead animals.