The humble house fly may seem like a minor nuisance, but it actually plays a serious role in transmitting disease.
A recent study  found that flies were responsible for spreading dangerous E.coli bacteria onto spinach leaves. The pathogenic bacteria survived on the flies for 13 days after they picked it up via contaminated cattle manure.
In 2010, researchers from the University of Florida (UF) collected house flies hovering around bins outside several different restaurants. They discovered 11 different pathogens  on the flies — all of which cause illness in humans, ranging from food poisoning to respiratory infections.
The researchers also found that while 200 types of bacteria had already been documented in flies, that number was likely to rise — and that they actually carry up to twice as many pathogens as cockroaches!
Flies seek out decaying food and waste, largely because it makes it easier for them to liquefy their food before ingesting it. Adding to the yuck factor, they spread bacteria in a few fairly unappetising ways, including regurgitating and secreting saliva as they liquefy their food, and defecating on food and surfaces which humans come into contact with. Yum.
While most people’s immune systems protect them from germs carried by flies, some are more susceptible to fly-related health risks — including infants, the elderly, and people with immune systems compromised due to illness or chemotherapy.
As such, it’s vitally important to think of flies in your residential pest control arsenal and take the necessary measures to ensure they don’t affect your family’s health.
 Transfer of Escherichia coli O157:H7 to spinach by house flies, Musca domestica (Diptera: Muscidae), Wasala L, Talley JL, Desilva U, Fletcher J, Wayadande A, April 2013, Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, USA. http://www.ncbi.nlm.nih.gov/pubmed/23425236
 UF discovers house flies carrying five new illness-causing bacteria, Mickie Anderson, 26 August 2010, University of Florida. http://news.ufl.edu/2010/08/26/flies/
The average house fly lives for about 15-25 days and longer in cooler climates, but it lays up to 3000 eggs in its lifetime — including on your food and theirs.
"A recent study found that flies were responsible for spreading dangerous E.coli bacteria onto spinach leaves. The pathogenic bacteria survived on the flies for 13 days after they picked it up via contaminated cattle manure."