Next time you’re hosting a barbecue, shooing away the house flies zipping around your just-grilled steaks and bowls of potato salad may take on more significance than merely brushing away an annoyance.

A study by University of Florida scientists has documented five more bacteria species carried by house flies – and all of them can cause illness in humans.

The bacteria cause illnesses ranging from food poisoning to respiratory infections.

The researchers collected house flies from rear entrances and trash bins at four restaurants. Twenty flies were collected from each location in sterile containers and taken back to the lab.

Using fatty acid analysis and DNA sequencing, the team identified a total of eleven pathogens carried by the flies – and five of those had not been previously linked to house flies.

The findings suggest that fly control must be taken seriously, especially around food.

In most cases, healthy adults have a good immune response to the pathogens.

But for other groups, such as infants, senior citizens and those whose immune systems are compromised by illness or chemotherapy, serious health problems can result.

Prior to the university’s study, there were about two hundred bacteria known to be carried by flies. The researchers said with more time, they’d likely find even more.

In addition to the eleven bacteria documented in the study, there were five others that couldn’t be positively identified, the researchers said.

Food safety experts say sanitation is still the best way to control flies in and around your home. Be careful to keep animal waste picked up and all garbage bins tightly covered and sealed.

It’s for your own good: Those house flies are carrying around more trouble than we thought.