Flies really do spread disease in humans, study confirms

We’ve suspected it for some time, but experts have confirmed that houseflies carry hundreds of different species of harmful bacteria and may help to spread disease.

With that in mind, the international team of researchers has warned people to avoid eating food that has been left out at picnics and to avoid picnics full stop in busy urban environments.

Results of a study at Penn State Eberly College of Science in the United States supports the long-held view that flies contribute to the rapid spread of disease in humans.

With that in mind, you might want to work at keeping houseflies out of your home.

Flies pick up bacteria from faeces and decaying matter and use it to nurture their young – also transmitting it to humans. Photo: Getty
Flies pick up bacteria from faeces and decaying matter and use it to nurture their young – also transmitting it to humans. Photo: Getty

According to The Spruce, the best way of getting rid of them is to ditch the things that are attracting the flies and providing food and breeding sites, which means: inspection, sanitation, exclusion, and mechanical and/or chemical control.

From keeping rubbish closed in lidded containers and cleaning up spills quickly, to keeping your pet food area’s clean, sanitation will reduce the chance of flies, it says, while exclusion is all about eliminating how they get into your house.

But once they get in, you can try either mechanical control like swatters or traps or go for a chemical solution.

While it might all seem a bit dramatic, experts behind the study published in the journal Scientific Reports said it might make people think twice about eating food that had been left out and exposed to flies and their diseases.

The study looked at microbiomes on 116 houseflies and blowflies from three different continents and researchers also investigated the microbes on individual fly body parts including legs and wings.

Stephan Schuster, research director at Nanyang Technological University, Singapore, said a fly’s legs appear to transfer the most microbial content from one surface to another.

Flies probably pick up the bacteria from faeces and decaying organic matter which they use to nurture their young, the study indicated.

Scientists found 15 instances of the human pathogen Helicobacter pylori – which causes ulcers in the human gut – on Brazilian blowflies.

“We believe that this may show a mechanism for pathogen transmission that has been overlooked by public health officials,” said Donald Bryant, Ernest C Pollard Professor of Biotechnology at Penn State University.

“It will really make you think twice about eating that potato salad that’s been sitting out at your next picnic.

“It might be better to have that picnic in the woods, far away from urban environments, not a central park.”

The study did suggest, however, that flies could help human society by serving as living “drones” or acting as early warning systems for disease.