Restaurant dishes and silverware may be an overlooked place where people can catch stomach viruses, according to a new study published today on the PLOS ONE website. While the current industry guidelines for cleaning dishware used in public settings are effective at neutralizing bacteria, researchers at the Ohio State University found that they appear to fall short of eliminating norovirus.
Norovirus is the leading cause of epidemic gastroenteritis and the major cause of foodborne illness worldwide, responsible for at least 50% of all gastroenteritis outbreaks in the United States.
“We know that when public food establishments follow the cleaning protocols, they do a very good job at getting rid of bacteria,” says Melvin Pascall, associate professor in the Department of Food Science and Technology at Ohio State. “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.”
Supported by a grant from the Ohio State Center for Clinical and Translational Science, Pascall and Jianrong Li, assistant professor of virology at Ohio State, led a team of virologists and public health experts to test the ability of the norovirus and common bacteria to make it through a variety of “real life” food service cleaning scenarios that included manual and mechanical washing.
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.
“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,” says Jianrong Li, assistant professor of food virology, who holds a joint appointment with the Department of Food Science and Technology (College of Food Agriculture and Environmental Sciences), and the Department of Environmental Health Sciences (College of Public Health). ‘”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.”
The scientists acknowledge that dairy products themselves could have protected the virus from heat and the sanitizing solutions. When the solutions were tested against MNV-1 in isolation, they were effective at killing more of the virus, but still not enough to eradicate the virus completely. Building off these research results, Pascall and Li’s team will next investigate if Hepatitis A and influenza viruses are able to get past current washing and sanitization protocols.
“Proper sanitation and handling remain the single biggest factor that can prevent cross-contamination of food and dishware at food service establishments," says Pascall. “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.”
Norovirus is responsible for 90 percent of epidemic non-bacterial cases of gastroenteritis and is commonly associated with illnesses seen on cruise ships and other “closed communities” where the virus can spread easily.
“Norovirus spreads rapidly through confined populations and can easily contaminate food or water. 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,” says Kurt Stevenson, professor of internal medicine and epidemiology in the Division of Infectious Diseases at Ohio State's Wexner Medical Center.
Stevenson, who was not part of the study, helped author guidelines for the Centers for Disease Control on preventing and controlling norovirus outbreaks in a healthcare setting, also noted that norovirus causes an estimated 91,000 emergency room visits and 23,000 hospitalizations for severe diarrhea among children under the age of 5.
Source: Ohio State University Center for Clinical and Translational Science