Restaurant dish washing has no effect on contagious stomach virus

Monday, December 17, 2012 by: David Gutierrez, staff writer
Tags: restaurants, washing dishes, stomach virus

(NaturalNews) Current dish washing practices in restaurants are completely inadequate for preventing the spread of one the most common agents of foodborne illness, according to a study conducted by researchers from Ohio State University and published in the journal PLoS ONE.

"We know that when public food establishments follow the cleaning protocols, they do a very good job at getting rid of bacteria," researcher Melvin Pascall said. "Now we can see that the protocols are less effective at removing and killing viruses - and this may help explain why there are still so many illnesses caused by cross-contaminated food."

The study focused on the spread of norovirus, a virus responsible for the majority of gastroenteritis epidemics in the United States, and 90 percent of non-bacterial gastroenteritis outbreaks. The virus is highly contagious and is well-known for causing "stomach flu" outbreaks on cruise ships and in other closed settings. It is responsible for approximately 91,000 emergency room visits each year, as well as 23,000 hospitalizations of children under the age of five for severe diarrhea.

"Norovirus spreads rapidly through confined populations and can easily contaminate food or water," said norovirus expert Kurt Stevenson, who was not involved in the study. "Numerous point-source outbreaks are attributed to contaminated water sources where food is grown and cultivated or through the improper handling of food by infected handlers."

Virus unaffected by dishwashing

To test whether standard food service cleaning practices are effective at removing norovirus, the researchers infused cream cheese and reduced fat milk with either murine norovirus (MNV-1) or with one of two forms of bacteria, Escherichia coli (E. coli K-12) or Listeria innocua (L. innocua). Dairy products were selected because they are known to be difficult to clean off.

The infused dairy products were spread onto glassware, ceramic plates and stainless steel utensils, which were then washed either with a commercial dishwasher or by hand. All washing made use of chlorine and quaternary ammonium compound (QAC)-based sanitary protocols.

Both hand and machine washing effectively reduced the levels of both bacterial species enough to meet safety thresholds, although dishes washed by hand were more likely to retain bacterial traces. Neither technique; however, significantly reduced the presence of norovirus at all.

"Even though the protocols were able to kill some of the virus, norovirus is highly contagious and it takes only a few viral particles to infect humans," researcher Jianrong Li, said. "These results would indicate that the neither the detergents nor sanitizers used in current cleaning protocols are effective against the norovirus at the currently used concentrations."

When tested in isolation, the cleaning agents did significantly reduce the concentration of norovirus, but still not enough to prevent contagion. This suggests that the virus is even more resilient when mixed with certain foods.

"Proper sanitation and handling remain the single biggest factor that can prevent cross-contamination of food and dishware at food service establishments," Pascall said. "However, it appears that we need to identify better agents or methods to significantly reduce the presence of norovirus and work to update the protocols."

Sources:

http://www.sciencedaily.com/releases/2012/12/121205195854.htm