Thinking about eating out this weekend? Maybe you should think again. Researchers from Ohio State University have found that the washing methods used by restaurants may not significantly reduce contamination of the norovirus - meaning that you could be put at risk for food poisoning this holiday season.
A study published in PLoS One conducted the study with ceramic plates, drinking glasses, and stainless steel forks. The researchers put cream cheese and reduced-fat milk on the surfaces, both of which are rather difficult to remove. The cream cheese and the milk were contaminated with the norovirus, as well as Escherichia coli K-12 and Listeria innocua, two strains of bacteria that also cause illness in consumers.
According to the study authors, "cross-contamination of ready-to-eat (RTE) foods with pathogens on contaminated tableware and food preparation utensils is an important factor associated with foodborne illnesses. To prevent this, restaurants and food service establishments are required to achieve a minimum microbial reduction of 5 logs from these surfaces." The study washed the items by hand and in the dishwasher using tap water, sodium hypochlorite, and quaternary ammonium, comparable to the materials used in a restaurant.
The researchers found that while E. coli and listeria could be sufficiently decontaminated using the sanitizing materials found in restaurants, norovirus could not be. At best, norovirus was reduced by 3 logs after washing. Machine-washed dishes fared slightly better, but still not enough to completely decontaminate the surface. Researchers theorize that norovirus was more resistant against washing and sanitizers compared to E. coli and listeria.
The news is perhaps all too familiar of the residents of Casper, Wyoming. The town has reported 167 self-reported cases of gastrointestinal illnesses in the past week. Evidence suggests that the illness has been linked to a Golden Corral restaurant, a buffet that opened in the area just a month prior to the outbreak. One diner who came down with norovirus, along with his entire family, said that he spotted dishes being served on dirty plates there, though they ate their meal anyway. He said that an employee informed them that the dishwasher was not working. Health inspectors who visited the restaurant after the outbreak said that they did not see unclean dishes and the dishwasher was working.
Norovirus is the most common cause of gastroenteritis and the major cause of food poisoning in the United States. It also accounts for half of the cases of gastroenteritis globally.