Skip navigation
Food Safety: To Reduce norovirus Risk, Assess the “Dirty Dozen"

Food Safety: To Reduce norovirus Risk, Assess the “Dirty Dozen"

Identify areas where contamination potential is highest and establish a program to keep them sanitized.

In the September issue, FM ran a column about the challenge of managing Norovirus risk by Jim Mann, Executive Director of the Handwashing for Life Institute, The column proved especially timely: several major Norovirus outbreaks received national attention that month with several occurring in prominent onsite institutions, including a major university in the Washington, D.C. area.

As Mann said at the time, Noroviruses are one of the most common contaminants associated with food safety incidents. Finding ways to reduce possible Norovirus cross-contamination potential should be a major focus of any operator concerned about food safety within his or her establishment.

Mann's organization has done a significant amount of research into those strategies that can be most effective in reducing Norovirus risk. To follow up the earlier column, we interviewed him about some of the ways FM readers can develop more effective risk prevention programs.

You've talked about the risk Norovirus contamination entails for operators. What's wrong with the way the industry deals with this today?

Mann: “One issue is that the focus in the past has most often been on the ill or unsanitary foodservice worker, with the assumption that most Norovirus contamination happens that way. But in fact, research shows that a great deal of Norovirus contamination comes in through the front door. To protect your facility, you need a broader, more integrated approach that goes beyond focusing only on staff.

“When you start dealing with the realities, what we have learned from the cruise ship industry, where Norovirus is a huge problem, is that contamination often begins with a guest. When visitors enter a restaurant or cafeteria, they do not stay very long. But what they leave behind can stay for some time. Norovirus can live on a hard surface for weeks, not hours.

“Also, when you look at typical efforts to sanitize tabletops, as only one example, we find they often do more to push germs around rather than truly sanitize these surfaces. Then consider all of the surfaces commonly touched by guests that are not sanitized on a regular basis — chair arms, restroom door latches and so on. These have the potential to be high transfer points.

“The issue is, germs can enter the establishment through the front door as well as through the back of the house. Our legal system, with its principle of strict liability, puts the liability for any outbreak on the operator. So it is in the operator's best interest to establish procedures that can limit any potential for cross contamination. A good risk prevention program is designed to do this.”

Why don't we hear about this more often?

Mann: “For one thing, Norovirus incidents are often mis-identified. Many times, when you hear about an organization or location where there is a ‘24-hour flu going around,’ the culprit is really a Norovirus outbreak. But it is much more acceptable to the accountable parties to describe this as flu because it suggests there is no one to blame and that nothing can be done about it.

“In fact, there is much that can be done. And today, as it is becoming easier to identify the cause of specific illnesses, the probability that Norovirus will be correctly identified as a cause of illness is increasing all the time.”

So how would an operator start to better address this risk?

Mann: “In the spirit of HACCP (Hazard Analysis Critical Control Points) programs, potential surface to hand contamination risks should be identified and then prioritized in terms of their relative potential to cause problems. We recommend that an operator first form a small team with representatives from the staff. In a larger organization this would mean someone from operations, quality assurance and risk management.

“The team should be charged with establishing an assessment of the highest risk surfaces in three key areas: the kitchen, the restrooms and the service area. We refer to this as the “Dirty Dozen” exercise, and have some checklists and recommendations for doing these surveys on our website (

“The idea is that the team use various observation and measurement techniques to identify the 12 most critical surface contact points in each of the three areas. Then, there are recommended procedures for distilling these 36 points down to a specific ‘Dirty Dozen’ that exist across the entire facility. Hundreds, if not thousands of actual daily and weekly touches are now distilled down to 12 critical surface areas. That makes developing a prevention strategy much more manageable.”

Once you've identified these areas, what's the next step?

Mann: “You incorporate actions to test and sanitize these areas into your everyday operating procedures. We believe that the use of ATP technology is a convenient and effective way to test for the amount of contamination that may be present. (see Mann's earlier column in the September FM or at the address below for more info on ATP technology). We like it because of its real-time feedback and for its training value.

“Getting employees to regularly test the surfaces in a science-based verification task tends to reinforce their understanding that invisible microbes pose a threat and that it is an important part of their job to manage that threat. They are thus better motivated both to clean surfaces correctly and to wash their own hands regularly. Keeping hands and surfaces cleaner keeps food safer.

Can you suggest any strategies for minimizing surface contamination in the first place?

Mann: “Again, it is helpful to look at the cruise ship industry. When you board a cruise ship today, the first thing passengers will see is a hand sanitizing station on the deck. They are given information about using it right then and there.

“Restaurants might consider something along that line in the guest reservation or waiting area. While operators are often reluctant to suggest that contamination issues might exist, a very constructive way of addressing this might be to ensure that staff and employees use it frequently in front of guests.

“Seeing a station and seeing staff using it could send a very positive message about your own operation. It suggests that what is being done in the front of the house likely to be managed in the back of the house as well. It also could serve to remind guests that they share in the responsibility for food safety, especially since many diners do not wash their hands immediately before being seated or eating.

“One last point is that such interventions can be much more effective today than they have been. New hand sanitizers have recently been introduced that are specifically formulated to kill Norovirus. Research is showing that some of these are definitely more effective than others and operators should evaluate them with this in mind. There are very significant differences in effectiveness.”

Jim Mann is the founder and Executive Director of the Handwashing For Life Institute, dedicated to helping operators set and achieve safe hand hygiene levels. Visit the website at or contact Jim directly at [email protected]

You can read Jim Mann's earlier column on Norovirus at this address:

For more information…

You can view information on Norovirus sanitation research at the following site, which also offers downloadable posters:

You can view information on the Center for Disease Control (CDC) vessel sanitation program at:

You can obtain useful Q&A handouts on norovirus from this CDC website:

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.