A dental office visit had me watching a few minutes of a talk show on the waiting room television. As I watched, the host talked about how dangerous bacteria was from reusable cloth grocery bags and showed the bacterial count taken from a swab test of an audience provided bag. Why was a swab test not also done on clothes worn by an audience member and compared to the reusable bag as a control? — bacteria and viruses are on many surfaces not just grocery bags. The answer of course was this was day time television and not a science show. Those of us who have winter and snow must surely be at risk from our winter coats as well. Public health authorities are continually telling us to wash our hands and cough into our elbows to reduce the risk of infection since we are all touch our faces after touching potentially infectious surfaces. What makes a grocery bag more dangerous than a door knob or an uncovered cough? Why are public health authorities not raising the alarm about cloth bags?
The recent paranoia about bacteria on grocery bags appears to be as a result of a study done by Klick and Wright of the University of Pennsylvania Institute for Law & Economics in 2012. http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2196481## With financial support from “Property And Environment Research Center.” http://perc.org
The paper was neither peer reviewed nor written by epidemiologists and many errors were pointed out by critics, including the Department of Health for San Francisco. http://blogs.berkeley.edu/wp-content/uploads/2013/02/SF-Health-Officer-MEMO-re-Reusable-Bag-Study_V8-FIN1.pdf and http://www.washingtonpost.com/blogs/wonkblog/wp/2013/02/16/is-san-franciscos-ban-on-plastic-bags-making-people-sick-perhaps-not/
Major mistakes made included assuming all cases of gastrointestinal bacterial infections were from people actually using the cloth bags in the first place and not properly separating other causes such as campylobacteriosis from e-coli. (The health memo is a good read.)
It also appears the paper was supported indirectly by the plastic industry itself. http://www.bagmonster.com/2013/03/study-claims-reusable-bags-are-deadly-scientist-disagrees.html and http://www.sourcewatch.org/index.php?title=Property_and_Environment_Research_Center
There has been one case of a disease spread from a dirty cloth grocery bag. The culprit was traced to a reusable grocery bag. http://www.nbcnews.com/health/reusable-grocery-bag-carried-nasty-norovirus-scientists-say-761983
Any article of clothing or bedding used by anyone infected with a norovirus could be a source for the disease. Common sense is to wash anything that has come into contact with an infection.
My conclusion is unless you are in the habit of letting raw chicken juices soak into your cloth bags and never wash your food carefully before preparation, you really have nothing to worry about with a cloth bag.