1) Kitchen utensils (such as knives and graters) can cross-contaminate foods with viruses, and vice versa.

2) Current dishwashing protocols are not always sufficient to destroy noroviruses on tableware.

These are the big take-home messages from two separate studies recently published by investigators who are part of the NoroCORE team. Researchers at the University of Georgia’s Center for Food Safety studied the transfer of Hepatitis A and Norovirus between fresh produce and kitchen utensils (knives and graters). They found that when using uncontaminated utensils on contaminated produce, the utensils then became contaminated and could spread the virus to additional produce that was cut/grated afterwards. When using contaminated utensils on uncontaminated produce, the produce often became contaminated. In other words, the virus could spread both ways (utensil to produce, produce to utensil, and back to produce). For more details, check out the news article at Medical Xpress.com or the summary in the Barfblog.

Researchers at the Ohio State University studied the efficacy of standard dishwashing methods on removing norovirus and bacteria from dirty tableware. Newswise.com provides the following excellent summary of the findings:

“To carry out the experiment, the research team infused cream cheese and reduced fat milk – two foods that are known for being difficult to clean off – with murine norovirus (MNV-1), Escherichia coli (E. coli K-12) or Listeria innocua (L. innocua). The scientists then applied the dairy products to stainless steel utensils, ceramic plates and glassware, and put the tableware through a variety of chlorine and quaternary ammonium compound (QAC)-based sanitary protocols delivered via a commercial dishwasher or hand washing.

The team found that while both the commercial dishwasher and manual washing reduced bacterial loads of E. coli K-12 and L. innocua enough to meet safety standards, neither technique was able to significantly reduce the presence of MNV-1. Overall, dishes that were hand washed were more likely to contain traces of both bacteria and viruses than those cleaned in a commercial dishwasher.”

Basically, current dishwashing methods/sanitizers aren’t up to the job of completely removing norovirus, at least from tableware soiled with this kind of food product. It is important to note that even though norovirus loads were reduced, it only takes a small number of particles to make someone sick, so partial reduction by washing/sanitizing is not sufficient to prevent illness. The original research paper is available at the PLOS one website.

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