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Annoying, yes, but will they also make you sick? UMass professor calls for more study of risk from houseflies

A housefly sitting on a flower budEPA

Here’s some disturbing food for thought when a housefly buzzes around your lunch. A University of Massachusetts Amherst professor is arguing that more attention needs to be paid to “synanthropic” flies — the non-biting flies that live alongside us — as potential disease carriers.

“Synanthropic flies may be even more important in disease transmission than blood-sucking flies,” John Stoffolano, professor of entomology at the university’s Stockbridge School of Agriculture, wrote in a review article that appeared last month in the journal Insects.

“Synanthropic flies have largely been ignored. Blood-feeding flies have taken the limelight, but we should pay attention to the ones that live among us because they get their nutrients from people and animals that shed pathogens in their tears, feces and wounds,” Stoffolano said in a statement from the university.


The article argues that the fly’s crop, a part of its anatomy where food is stored before being digested, may be “a deadly source of infectious pathogens” and deserves more study.

There’s evidence that flies can spread germs either by being eaten or by dumping “newly acquired pathogens/parasites” on food, either by regurgitation from the crop, defecation, or both, the article found.

A common house fly, for example, may feed on dog feces on the sidewalk before flying into your house, landing on your sandwich, and regurgitating germs there from its crop, the statement said.

More research is needed, the article suggested, to get “a better understanding and development of whether these flies are involved in emerging infectious diseases. If so, epidemiological models in the future might be better at predicting future epidemics or pandemics.”

“It’s the little things that cause the problems,” Stoffolano said in the statement. “Our health depends on paying closer attention to these flies that live with us.”

Martin Finucane can be reached at