Scientists have discovered that flies carry more diseases than suspected.
The house fly and the blowfly together harbour more than 600 different bacteria, according to a DNA analysis.
Many are linked with human infections, including stomach bugs, blood poisoning and pneumonia.
Flies can spread bacteria from place-to-place on their legs, feet and wings, experiments show. In fact, every step taken by a fly can transfer live bacteria, researchers said.
DNA sequencing techniques were used to study the collection of microbes found in and on the bodies of the house fly (Musca domestica) and the blowfly (Chrysomya megacephala).
The house fly was found to harbour 351 types of bacteria. The blowfly, which is found in warmer climates, carried 316. A large number of these bacteria were carried by both types of fly.