Houseflies do not need to bite us to transmit disease. They transfer bacteria and other germs from rotting substances and excreta to foodstuffs. When they sit on garbage, the bacteria get stuck on their wings, mouth and other body parts. And when they sit on the food stuff they leave the bacterium in them. This is how they transmit illnesses such as food poisoning, dysentery, typhoid and diarrhea. They are mere carriers of the various disease causing bacteria. Some of them are known to be carriers of diseases like anthrax, conjunctivitis, dysentery, typhoid, and fever.