You may have thought your diet of Chinese food was garbage, but common houseflies have a liquid diet composed quite literally of trash, like rotting garbage, animal waste and the thousands of germs that accompany them.
When these delectable liquid foods are not available, flies break down solid foods with digestive enzymes in their saliva and puke, then slurp it back up. So, yes, that fly that just landed on your freshly grilled burger loaded with pickles, crispy lettuce and tomatoes have probably just done its business. If it was a female, it may even have laid eggs on your barbecue bites. When flies land, they deposit bacteria from the last place they landed, which was probably a pile of animal feces.
These pesky common houseflies can carry at least 65 different diseases including cholera, typhoid, salmonella and even anthrax, according to researchers at the University of Pennsylvania.
So, should you still eat that buttery filet mignon you cooked to a perfect medium rare? Turns out, if you swat the fly away quick enough, the bacteria don’t have enough time to transfer to your food. Even if they do, our bodies are usually able to fight off whatever minor amount of bacteria may be consumed.