Epidemiology in the News: Norovirus


Foodborne disease is one of the preventable diseases and yet highly prevalent in the society due to lack of or less stringent healthy sanitary measures including the lack of provision of extended paid sick leave for food service workers. There is no doubt that no preventative or control measures can assure 100% proof in the elimination process of foodborne diseases. However, it is not intractable to establish optimal standards sufficient in minimizing foodborne diseases. Norovirus is one of the pathogens in the group of foodborne pathogens associated with gastro-intestinal infection (Aleccia, 2014a). This review explores the events associated with the recent Norovirus cases reported in the Explorer Cruise Ships and other food environment areas.

 Epidemiology in the News: Norovirus

            Norovirus is a foodborne disease. The virus is a gut-specific bug. The bug can be found in less exotic places including restaurants and many food environments. Norovirus is the leading cause of foodborne outbreaks in the US and perhaps around the world (Aleccia, 2014a). The virus spreads from an infected person to an uninfected person via poor sanitary (lack of washing of hands) inclination or the lack of frequent use of gloves in food preparation or by food service workers (Aleccia, 2014a). Based on the US National Outbreak Reporting System (NORS), the past four years’ data suggested that Norovirus spreads via the fecal-oral route (Aleccia, 2014a). The virus requires a small amount contaminants or particles to initiate pathological effects. One out of five food workers that come to work sick with the virus, transmits and propagates the virus to others via food contamination (Aleccia, 2014a).

In January 2014, the virus sickened about 700 people cruising with the “Explorer of the Seas” cruise ship (Aleccia, 2014b). In the US, Norovirus accounts for about 25% of 20 million yearly cases associated to a family of viruses linked to acute gastro-intestinal distress (Aleccia, 2014a). From 2009 to 2012, 1008 outbreaks of Norovirus were reported in 43 states in the US (Aleccia, 2014a). About 50% of the reported outbreaks were cases with single known cause (Aleccia, 2014a). For the non-food related Norovirus outbreaks, 80% occur in nursing homes and long-term care facilities, and only 1% is linked to Cruise Ships (Aleccia, 2014a).

Restaurant settings account for two-thirds (67%) of Norovirus outbreak (Aleccia, 2014a). The second source settings for the pathogen is banquet and catering sites. Out of 520 outbreaks with a known medium of transmission, 70% medium of transmission was via food service workers (Aleccia, 2014a). More than 50% of the cases involves direct contact with bare hands with ready-to-eat food by food service workers. About 70% cases of raw food are contaminated during food preparations. Food environment is always prone to contamination during and after the preparation process.

The measures of disease frequency and descriptive epidemiology described above were very informative about the sources and transmission mode of action of Norovirus. In a review, health officials suggested that it is crucial for policy makers and employers to extend paid leave programs for food service workers (Aleccia, 2014a; Aleccia, 2014b). The additional steps of paid leave will minimize risks associated with sick food service workers. Though, one of the critical information lacking from the review is the incubation period of the pathogen from the time of exposure to the time the symptom shows. The Asymptomatic and fatality rate of an untreated event was not included in the review. Hence, asymptomatic individuals capable of transmitting the pathogen poses a high risk to the public.


Aleccia, J. (2014a). Norovirus:Think restaurants, not cruise Ships, cdc says. Retrieved from http://www.nbcnews.com/health/health-news/norovirus-think-restaurants-not-cruise-ships-cdc-says-n121401

Aleccia, J. (2014b). We made it! Nearly 700 sick as illness plagued cruise Ship returns. Retrieved from http://www.nbcnews.com/health/health-news/we-made-it-nearly-700-sick-illness-plagued-cruise-ship-n18766