Penn State Eberly College of Science have found house flies can carry Salmonella, E. coli and even bacteria which can lead to stomach ulcers and fatal sepsis. The research, published in Scientific Reports, says flies may have been overlooked by public health officials as a source of disease outbreaks.

The paper found that fly’s legs transferred most of the microbial organisms from one surface to another, suggesting even a brief step onto food could leave behind bacteria. Flies in urban areas were found to carry more bacteria than rural flies, with the scientists suggesting avoiding city parks for picnics and, instead, eating food in more rural locations.

”People had some notion that there were pathogens that were carried by flies, but had no idea of the extent to which this is true and the extent to which they are transferred.” said Dr. Donald Bryant, Professor of Biotechnology at Penn State University.

Maksud Khan of Satna, Madhya Pradesh in India, arrived at the hospital experiencing stomach pains that doctors presumed was food poisoning, but an endoscopy revealed the cause to be metal objects.

Those objects — 236 coins, 100 nails, dozens of razor blades, a 6-inch piece of a rusted iron shackle, four needles, and a few glasses pieces — were found in the man’s stomach.

Khan’s relatives said he was suffering from depression, which may have triggered the habit.