Norovirus – Credit CDC PHIL
Lagniappe – A little something extra given to a customer.
# 6766
The CDC estimates that norovirus (aka the `Winter Vomiting Bug’ or less accurately, `Stomach Flu’) causes more than 20 million cases of gastroenteritis each year in the United States. Anyone who has endured it can attest that a bout with norovirus is misery incarnate.
The CDC maintains an extensive Norovirus webpage where they describe the illness, how it is spread, and how to avoid infection. Among known causes of foodborne illness, norovirus is the largest culprit.
The CDC’s NOROVIRUS: FOR FOOD HANDLERS page warns:
The virus can easily contaminate food because it is very tiny and infective. It only takes a very small amount of virus particles (fewer than 100) to make someone sick.
Food can get contaminated with norovirus when:
- infected people who have stool or vomit on their hands touch the food,
- it is placed on counters or surfaces that have infectious stool or vomit on them, or
- tiny drops of vomit from an infected person spray through the air and land on the food.
All of which makes the thorough cleaning of plates and utensils used in restaurants a priority.
According to a PLoS One study, published yesterday, the prescribed methods of cleaning these items in restaurants does a good job against common bacteria – like Escherichia coli K-12 and Listeria innocua – but not so well in sanitizing against norovirus.
The open access study is called:
Efficacies of Sodium Hypochlorite and Quaternary Ammonium Sanitizers for Reduction of Norovirus and Selected Bacteria during Ware-Washing Operations
Lizanel Feliciano, Jianrong Li*, Jaesung Lee, Melvin A. Pascall*
Abstract
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.
This study evaluated the sanitization efficacies of ware-washing protocols (manual and mechanical) used in restaurants to clean tableware items. Ceramic plates, drinking glasses and stainless steel forks were used as the food contact surfaces. These were contaminated with cream cheese and reduced-fat milk inoculated with murine norovirus (MNV-1), Escherichia coli K-12 and Listeria innocua.
The sanitizing solutions tested were sodium hypochlorite (chlorine), quaternary ammonium (QAC) and tap water (control). During the study, the survivability and response to the experimental conditions of the bacterial species was compared with that of MNV-1.
The results showed that current ware-washing protocols used to remove bacteria from tableware items were not sufficient to achieve a 5 log reduction in MNV-1 titer. After washing, a maximum of 3 log reduction in the virus were obtained. It was concluded that MNV-1 appeared to be more resistant to both the washing process and the sanitizers when compared with E. coli K-12 and L. innocua.
Essentially, these researchers took silverware, ceramic plates, and glassware – inoculated them with norovirus, E. coli, and Listeria – and ran them through standard dishwasher or hand washing protocols with either a bleach solution or quaternary ammonium compound (QAC) solution.
After that, they tested them for residual pathogens.
Although commercial dishwashers did a better job than did handwashing, with both, significant contamination from the norovirus remained behind.
The authors write:
Conclusions
From the results of our study, it could be concluded that QAC and sodium hypochlorite sanitizers normally used to inactivate bacteria in manual and mechanical ware-washing operations were unable to produce the same level of virus inactivation under similar conditions, irrespective of the nature of the tableware item tested.
Further studies are needed to develop more effective ware-washing protocols for the removal of viruses from food contact surfaces/tableware items. Also, the combination of different detergents and sanitizing solutions (especially those containing surfactant agents) should be evaluated since they may help to enhance the removal and inactivation of non-enveloped viruses.
Obviously, people who are sick should not be handling food, but people can shed the virus even after they stop showing symptoms.
So one of the keys to prevention is good hand hygiene.
Unfortunately, unlike with many other bacteria and viruses, alcohol gel doesn’t do a particularly good job of killing the virus, something we discussed last year in CMAJ: Hand Sanitizers May Be `Suboptimal’ For Preventing Norovirus.
Which makes a good old fashion hand scrubbing with soap and water the best preventative.
The CDC recommends the following steps to protect yourself from the virus.
And of course, the obvious question is . . .if norovirus escapes routine dishwashing protocols, what about other viruses like Hepatitis A and influenza?
Reportedly, these researchers will be looking at those viruses next.
