The CDC’s new Vital Signs report on noroviruses – NoroCORE Food Virology

The CDC’s new Vital Signs report on noroviruses

CDCVitalSignsNoroThe news media has been abuzz these past 24 hours following a new Vital Signs report released by the CDC that focuses on noroviruses, particularly their prevention in the food service industry. Here, we try to break down what this report means and why it is important.

What is a Vital Signs report?

Each month, the CDC releases a collection of materials in both English and Spanish related to a specific health issue. For this month’s Vital Signs on noroviruses, these materials included an early MMWR (Morbidity and Mortality Weekly Report) release, a comprehensive website, a factsheet, a podcast, a PSA, an infographic, information for the news media, and things to be posted on social media to raise awareness.

Where does the CDC get its information?

The CDC collects and analyzes large amounts of data on a wide variety of diseases and health concerns that affect people in this country. For this Vital Signs in particular, they integrated what had been learned from past research and practices with a new study that analyzed both suspected and confirmed foodborne norovirus outbreaks in the US from 2009-2012. This information was reported by state, local, and territorial health departments to the CDC through the National Outbreak Reporting System (NORS). In that four-year period, 43 states submitted information about 4,318 norovirus outbreaks, 1,008 of which had foodborne transmission cited as the primary cause.

What did they find? A pie chart of norovirus outbreaks

Here are some of the highlights in the MMWR article:

  • Among foodborne norovirus outbreaks that were connected with the preparation of food, 64% of them occurred in restaurant settings.
  • Out of 520 norovirus outbreaks that were associated with contaminated food, food workers were implicated 70% of the time. Bare-handed contact with ready-to-eat foods was found in over half of these food worker-implicated outbreaks.
  • Out of 324 outbreaks where at least one specific food was implicated, 92% of the time it was believed to occur during the food’s preparation, and the majority of the time it was for foods served raw (75%).
  • In 67 of these 324 outbreaks where a single food was found to be the cause, the most common food types were vegetable row crops (such as leafy vegetables) at 30%, fruits at 21%, and mollusks at 19%.
  • While most norovirus outbreaks that receive laboratory confirmation and virus typing are found to be caused by GII.4 noroviruses (66%), this is not the case for foodborne outbreaks.
  • The majority of non-foodborne norovirus outbreaks (80%) between 2009 and 2012 occurred in long-term care facilities.

Why is this information important?

In all reported US foodborne outbreaks where a single agent is found, 48% of the time they are caused by noroviruses, making them the leading cause of foodborne outbreaks in this country. Based on the data, the most common source is infected food workers that contaminate food during preparation.

While the majority of norovirus cases come from person-to-person contact (69% based on the new NORS findings), foodborne transmission in food service settings is important not only because noroviruses are the leading cause of foodborne illness, but because one infected person handling food has the potential to impact a large number of people. There are also specific steps that can be taken to avoid spreading the virus through foods.

What suggestions did the CDC make?

The CDC presented several suggestions each for the state and local governments, the food service industry, food service workers, and the general public.

The CDC is stressing good hand hygiene for everyone, which you can read more about here.

They also stress excluding ill food service workers from work until at least 48 hours after the person is no longer experiencing symptoms, as well as thorough cleaning and disinfection practices in food establishments and avoiding bare-handed contact with foods.

For managers in the food service industry, they suggest certification in food safety practices as a method that has been associated with fewer norovirus outbreaks. The CDC also recommends providing food safety training to food service staff, and providing sick leave and other programs that promote ill workers staying home.

Lastly, the CDC calls for more thorough investigation and reporting of outbreaks on the part of the state and local governments, and broader adoption and enforcement of the FDA’s Food Code.

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