House flies transmit organisms that cause diseases such as tuberculosis, yaws, leprosy myiasis and poliomyelitis. House flies can also transmit parasitic worms such as Pinworms, Roundworms and Hookworms. House flies pick up disease causing organisms from garbage, sewage and feces. They then transfer these organisms to human and animal food by regergitation, defication or simply carrying them on their legs or in their mouths.