It is imperative to wash re-usable grocery bags.

There are actually a variety of bacteria and viruses, such as E-coli and salmonella, which can be spread through the use of grocery bags as they come in contact with so many bugs.

Raw meat, unwashed produce, and public surfaces in addition to the fact that many bags are made of fabrics which can harbor disease.

The simple solution is to wash and dry bags to eliminate any chance of contamination.

While the risk of contracting an illness from any particular reusable bag is low, Schaffner said, the Oregon study follows a 2010 paper by researchers at the University of Arizona and Loma Linda University that found large numbers of bacteria in reusable grocery bags, including 12 percent that were contaminated with E. coli.
When scientists stored the bags in the trunks of cars for two hours, the number of bacteria jumped 10-fold.