CDC Telebriefing – New Vital Signs Report: How can we prevent norovirus outbreaks from contaminated food?

OPERATOR: I'd like to thank all participants for holding.  All lines will be on listen only until the question and answer portion of this conference. I’d also like to inform all participants today’s conference is being recorded.  I'd like to turn the call over to Tom Skinner.  Thank you.  You may begin. 

TOM SKINNER:  Thank you, Bryan.  And thank you all for joining us today for the release of another Vital Signs report from CDC, this one on foodborne norovirus outbreaks, United States 2009 to 2012.  With us today is the Director of the CDC, Dr. Tom Frieden who's going to provide some opening remarks and then he'll be leaving the call.  And with us to answer your questions is Dr. Aron Hall.  That's spelled a-r-o-n, h-a-l-l.  He's with our Division of Viral Diseases here at CDC.  I'd like to turn the call over to Dr. Frieden. 

TOM FRIEDEN: Thank you all for joining us to discuss this month's Vital Signs report.  Every month we focus on the latest data about critical health issues that face our country and what we can do about it.  This month we're addressing norovirus outbreaks caused by contaminated food.  Now, a lot of people have heard of norovirus because it's what usually causes outbreaks on cruise ships.  What's much less well known is that those outbreaks only account for about one percent of all reported norovirus outbreaks.  Norovirus is extremely contagious and it can cause outbreaks anywhere people get together, anywhere food is served.  And it makes people sick with vomiting and diarrhea.  Every year about 20 million people get sick from norovirus.  Most either have contact with people who have the infection or eat contaminated food.  In fact, norovirus is the leading identified cause of outbreaks from contaminated food in the U.S.  According to today's CDC Vital Signs, most of the reported norovirus outbreaks from contaminated food occur in food service settings.  Food service workers who are infected and yet continue working are often the source.  The food service industry has a crucial role to play helping prevent norovirus outbreaks from contaminated food.  A lot more can be done to increase food safety and ensure that food service workers adhere to food safety laws, regulations and guidelines.  The Vital Signs report includes outbreak data which was submitted by state, local and territorial health departments from 2009 to 2012.  Key findings included the following:  Most of the norovirus outbreaks occurred in food service settings.  That includes restaurants, which accounted for nearly two-thirds of documented outbreaks, and catering or banquet facilities which accounted for 17 percent.  Food workers who were infected with norovirus were associated with about 70 percent of the reported outbreaks from contaminated food where factors contributing to contamination were identified.  More than half of those involved touching ready-to-eat food with bare hands.  Ready-to-eat food that are ready to be served without additional preparation such as washed, raw fruits and vegetables for salads or sandwiches, baked goods or items that have already been cooked.  Bare hand contact with food is something that is recommended not to happen in restaurants and can make you sick.  Of the reported outbreaks in which a specific food item was implicated, more than 90 percent were contaminated during final preparation.  The reason for that is that the infectious dose of norovirus is tiny.  You only need a minuscule dose, a tiny number of virus particles, to become infected.  Some key recommendations to help the food service industry prevent norovirus outbreaks are included in the Vital Signs report.  These underscore provisions in the Food and Drug Administration, Model Food Code and CDC guidelines.  And they include the following:  Make sure food service workers practice proper hand washing and use utensils or single use disposable gloves to avoid touching ready-to-eat food such as raw fruits and vegetables with their bare hands.  Certify kitchen managers and train food service workers in food safety practices.  And establish policies that require food service workers to stay home when they're sick with vomiting and diarrhea and for at least 48 hours after symptoms stop.  Some food service workers understandably fear losing their job and also leaving co-workers short staffed if they don't go to work when they're sick.  That's why it's so important that businesses consider using measures that encourage workers to stay home when they're sick.  That includes paid sick leave and a staffing plan that includes on-call workers.  The report also highlights the important role health departments play investigating, reporting and stopping norovirus outbreaks.  And the continued need to build their capacity to do this even more thoroughly.  If we have better lab capacity through tools such as advanced molecular detection, we can quickly find, track the source and stop norovirus outbreaks using things like genome sequencing and analysis.  Another thing to note is that outbreak reporting varied enormously from state to state during the four-year period covered in the report.  But that's probably more a matter of difference in how hard states are looking rather than how much disease is there.  Improving or monitoring efforts will help us to better identify sources of norovirus outbreaks from contaminated food and to improve prevention strategies.  The bottom line is that norovirus is one tough bug.  Norovirus infections are sometimes called food poisoning, but actually norovirus comes from people.  So food service workers who are infected and have bare hand contact with your food can contaminate it during preparation.  And policies implemented by the food service industry can make a big difference in reducing that risk.  Because norovirus outbreaks often occur in food service settings, businesses, kitchen managers, food service workers have really important roles to play in preventing the spread of norovirus.  More can be done.  The food service industry can help prevent norovirus outbreaks from contaminated food by fostering a work environment that promotes and adheres to recommended food safety practices and outlined in the FDA, Food Code, and CDC guidelines.  We do know how to stop norovirus from contaminating our food, and there's nothing worse than going out to eat and coming back with, instead of a good meal, an illness that's going to last you a few days and make you very sick.  Because the infection is -- because the virus is so infectious, it's important that there is scrupulous hand washing.  We know how to stop it; we just need to do it.  Everyone should be able to go out to eat without worrying about whether their food is safe.  I'll turn this back over to Tom Skinner and Dr. Hall. 

TOM SKINNER: Bryan, I think we're ready for questions. 

OPERATOR: Okay.  At this time, if you would like to ask a question, press star 1.  Please record your name when prompted.  Once again, star 1 to ask a question.  Okay.  First question comes from Lenny Bernstein, Washington Post.  Your line is open. 

LEONARD BERNSTEIN: Hi, Dr. Hall.  Thanks very much for taking my question.  I'm actually going to ask you two.  The first one is pretty easy.  I assume the norovirus lives in the gut?  Is that where it originates? 

ARON HALL: Yes.  People are the only known reservoir of norovirus.  And it infects our small intestine.  And so that's where it propagates.  And then is shed through feces and vomit. 

LEONARD BERNSTEIN: Okay.  The other is a math question.  I'm a little confused.  I'm reading from the results of the report.  It says that during '09 to '12 a total of 4,318 outbreaks were reported to NORS resulting in 161,000 illnesses, et cetera.  Then it says foodborne transmission was the primary mode reported in 1,008.  So if foodborne transmission is the vast majority of these, what's -- what are the other 3,310?  Where are they coming from? 

ARON HALL: So, in fact, the most commonly reported route of transmission in norovirus outbreaks is direct person-to-person spread.  Followed by foodborne transmission in about 23 percent of reported foreign outbreaks.  Most of the outbreaks not foodborne associated are associated with healthcare settings and there are existing guidelines to help in those settings.  In this issue of Vital Signs we’re focusing specifically on foodborne norovirus outbreaks because we feel there's a great opportunity for prevention. 

TOM SKINNER: Do you have a follow-up, Lenny?  Next question, Bryan? 

OPERATOR: Next question, John Tozzi, Bloomberg. Your line is open. 

JOHN TOZZI: Hi.  I'm wondering, is there any research into whether places that have paid sick leave policies have lower rates of reported norovirus outbreaks? 

ARON HALL:  So we do know from surveys with restaurant workers that some of the key barriers to keeping them home while sick include their concerns about leaving fellow workers short staffed as well as not getting paid.  So overcoming that barrier by providing sick pay and providing on-call staffing plans may help tremendously in keeping sick workers at home. 

TOM SKINNER: Do you have a follow-up? 

JOHN TOZZI: No.  I mean, that's helpful.  But it sounds like that we don't know of any kind of concrete research tying the policy in a city or country or wherever of paid sick leave to lower recorded levels of outbreaks. 

ARON HALL: Yeah.  Those data are not included in this report.  But one item that is noted in this report is that the presence of certified kitchen managers has been associated with a lower incidence of norovirus outbreaks.  And so that's one key prevention step that restaurants can take to help reduce the incidence. 

JOHN TOZZI: Okay.  Thank you. 

TOM SKINNER: Next question, Bryan? 

OPERATOR:  Lisa Schnirring, CIDRAP News.  Your line is open. 

LISA SCHNIRRING: Hi.  Thanks for being available to take questions today.  I heard this statistic that 90 percent of the food-related outbreaks relate to contamination on finished food products.  Are there certain products that seem to be more associated with it?  Or is it one of those equal opportunity contaminants?  My other question is, you hear about this a lot.  And how -- how -- how much do the surveillance systems capture these kind of outbreaks?  Do you think that your numbers today are kind of a conservative estimate?  Or do you think that -- that things are becoming more detected over the years?  Just any thoughts on that would be helpful.  Thanks. 

ARON HALL: Thank you.  So your first question first.  We did identify that among outbreaks in which a food was implicated, 92 percent involved foods contaminated immediately prior to service.  So during preparation.  And essentially any food can become contaminated with norovirus if it's handled after it's been cooked.  So the most common foods that are identified include things that are ready to eat such as salads and sandwiches.  But any type of food can be contaminated if an infected worker is handling it after it's been cooked.  With regard to surveillance, we do know that what gets reported is probably just the small tip of the iceberg of what's occurring out there.  There is significant variation in reporting between the states, as Dr. Frieden noted in his introductory remarks.  We think what gets reported is probably a snapshot and likely an underestimate of the true incidence of foodborne norovirus outbreaks. 

TOM SKINNER:  Next question, Bryan . 

OPERATOR:  Next question, Kathleen O’Brien.  Star Ledger. Your line is open. 

KATHLEEN O’BRIEN: Hi.  I just wanted to make sure I understood the scope of what we're looking at today. We're looking at foodborne norovirus illnesses.  But they constitute really a small -- relatively small slice of the -- I believe you said 20 million cases of norovirus every year?  Is that -- do I understand that correctly? 

ARON HALL:  The overall burden of norovirus in the United States is about 20 million cases per year.  And those cases result from either direct contact with infected people or consumption of contaminated food.  Foodborne outbreaks alone, we report over 1,000 have occurred over the last four years. 

TOM SKINNER:  Do you have a follow-up? 

KATHLEEN O’BRIEN:  1,000 incidents or 1,000 people?  1,000 cases or 1,000 incidents with each one affecting 200 diners?  It seems like -- it seems like we are looking at kind of a small slice, and essential small slice, but a small slice of the 20 million.  

ARON HALL:  So what's summarized in this report are outbreaks caused by norovirus.  And we know that outbreaks are, indeed, a small segment of the overall burden of disease.  But these are the situations where we can learn the most about transmission and exposures.  And it's from this information that we can identify the foods that are implicated and the sources of those infections, including infected food workers for these outbreaks occurring in restaurants.  And so with the information from outbreak surveillance, we can make informed decisions about how best to prevent transmission. 

KATHLEEN O’BRIEN: Thanks. 

TOM SKINNER: Next question, Bryan? 

OPERATOR:  Before we take our next question, once again, star 1 to ask a question.  Next question, Joette Giovinco, WTVT. 

JOETTE GIOVINCO: Thank you for taking my call.  I have a really practical question.  On one of the fliers that you sent out it talks about washing fruits and vegetables.  And I think previously someone had said either the prepackaged, prewashed we shouldn't rewash.  Could you just clarify that for just our general public? 

ARON HALL:  So our recommendations for preventing the spread of norovirus through food are to wash and rinse fresh fruits and vegetables before consumption. 

JOETTE GIOVINCO: Would that also include the prepackaged, prewashed lettuce and various things we get at the grocery store?  I think we've been told previously not to wash those. 

ARON HALL: Yeah.  I think in order to prevent the spread of norovirus; the most prudent measure would be to wash any raw, ready-to-eat food immediately prior to consumption.  Including fresh produce that's already been rinsed. 

​[Editorial note: Many pre-cut, bagged, or packaged produce items like lettuce are pre-washed and ready-to-eat. If so, it will be stated on the packaging. If the package indicates that the contents are pre-washed and ready-to-eat, you can use the produce without further washing but make sure to wash your hands before handling the produce. If you do choose to wash a product marked “pre-washed” or “ready-to-eat,” be sure to wash your hands before preparing it and use food safety practices to avoid any cross contamination.]

JOETTE GIOVINCO: Okay.  Thank you.  And should we just -- for people at home that may be ill, should we also tell them not to prepare food for their families?  To wait that 48 hours and to do the same types of things we're asking the food service employees to do as well? 

ARON HALL:  Absolutely.  The recommendations that we’re making for food workers really could apply to anyone who might be making food for their families, friends or communities.  We recommend that anyone who's preparing food not do so if they're ill with vomiting or diarrhea.  And for at least 48 hours after their symptoms have resolved.  

JOETTE GIOVINCO: Thank you very much. 

OPERATOR:  Next question.  Mike Stobbe with AP.  Your line is open. 

MIKE STOBBE:  Hi.  Thanks for taking my question.  Just following Kathleen O’Brien’s question, it was confusing.  Your estimate is 20 million of these illnesses a year, is it that 23 percent of those or about 4.6 million are foodborne, do you think?  Is that the proportion of the 20 million you think is attributed to -- spread through food or food handling? 

ARON HALL:  So the overall burden of illness caused by norovirus that estimate of 20 million, that's including every route of transmission.  For outbreaks is where we can get the best sense of the most common ways in which things are being -- norovirus is being spread.  And from outbreak surveillance, we see that 23 percent are caused by foodborne transmission.  However, norovirus is the leading cause of foodborne disease outbreaks responsible for 48 percent of all foodborne disease outbreaks reported in the United States.  And as the leading cause, it merits specific attention to protect the public and to make food safe. 

MIKE STOBBE:  I'm sorry.  So give us your best guess of how many of those 20 million are from foodborne. 

ARON HALL:  So CDC has estimated previously that the overall burden of foodborne norovirus is on the order of 5.5 million cases annually.  And in this report, we're highlighting specifically foodborne norovirus outbreaks. 

MIKE STOBBE:  Okay.  Did you say 5.5 million, though, is a ballpark estimate? 

ARON HALL:  Correct. 

MIKE STOBBE:  Okay.  Thank you. 

TOM SKINNER:  Next question, please. 

OPERATOR:  Matthew Glasser, NBC.  Your line is open. 

MATTHEW GLASSER: Yes, thank you.  In California they passed a glove law that mandates that restaurateurs use gloves for ready-to-eat food.  It immediately got a huge amount of backlash for restaurant owners.  They're working on repealing it as we speak.  What are your thoughts when states try to do the right thing but then get backlash from the restaurant industry in terms of glove use? 

ARON HALL:  So our recommendations for the food service industry as well as local government are to follow stipulations in the FDA food code.  Those do include eliminating bare hand contact with ready-to-eat foods.  There are a variety of ways in which food workers can do this.  One of which is by wearing gloves.  But they may also do so through the use of utensils.  And these methods can help prevent contamination from bare hands to ready-to-eat foods. 

MATTHEW GLASSER: Is it concerning to the CDC to see that there was such a rapid backlash to the glove law? 

ARON HALL:  I think our recommendations follow closely that -- with those that have been made by many other public health agencies at state and local government as well as our colleagues at FDA.  Which recognize the need to eliminate bare hand contact with ready-to-eat foods?  And we are looking to work with the food service industry to help promote these practices. 

TOM SKINNER:  Next question, please.  Bryan, are there any additional questions? 

OPERATOR:  Yes.  Just got a question.  Isolda Peguero from Telemundo. 

ISOLDA PEGUERO: Hi.  Good afternoon.  Thank you for taking my question.  We were wondering, now that summer vacations are starting and a lot of people are taking cruises, traveling, you know, through airplanes, is there any specific concern or measures that should be taken to prevent the noroviruses spreading through those venues?  Or is there a small chance of that happening? 

ARON HALL:  Thank you.  So norovirus outbreaks occur in a variety of settings.  Cruise ships represent about one percent of all those outbreaks reported to CDC.  The recommendations of good hand hygiene and avoiding work while ill would apply year-round and across all of these settings.  So we recommend implementation of these measures throughout the year.  And particularly when folks are gathering or preparing food for others. 

ISOLDA PEGUERO: I have a follow-up question.  I just think it would be common sense if you're sick and you're a worker, especially a restaurant worker preparing food that you would wash your hands or call in sick.  How can we monitor that, in fact, those common sense measurements are put into place? 

ARON HALL:  Yeah.  So one step that restaurants can take is by getting proper training in food safety for their restaurant managers.  These certified kitchen managers who have received food safety training, their presence in restaurants has been associated with both a reduction in incidence of norovirus outbreaks as well as a reduction in bare hand contact with ready-to-eat foods as a contributing cause of outbreaks.  So this is one way in which getting the proper training and having the appropriate supervision can help improve food safety. 

ISOLDA PEGUERO: Thank you. 

TOM SKINNER:  Next question, Bryan? 

OPERATOR:  At this time, we have no further questions. 

TOM SKINNER:  All right.  We're going to ask Dr. Hall to conclude our call. 

ARON HALL:  I want to thank you all for taking the time to attend this telebriefing and to hear our messages about foodborne norovirus outbreaks.  I would like to reinforce that norovirus is the leading cause of disease outbreaks from contaminated food in the United States.  That infected food workers are the most common source of norovirus outbreaks from contaminated food.  And that CDC is calling upon the food service industry to work with us and local public health partners to prevent norovirus outbreaks. 

TOM SKINNER:  Okay.  Thank you, Bryan.  Thank you all for joining us.  This concludes our call today.  A transcript of this telebriefing will be made available on the CDC media relations website as soon as possible.  Reporters with additional questions or need for more information can call the CDC press office at 404-639-3286.  Thank you. 

OPERATOR:  Thank you.  That does conclude the call for today.  Please disconnect your phone lines at this time.  

###
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES