Analyses of the eFORS (Electronic Foodborne Outbreak Reporting System) Surveillance Data (2000-2004) in School Settings

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Introduction

Health and Economic Burdens of Foodborne Illness

Frequently cited statistics indicate that the health and economic burden of foodborne disease is a serious public health problem. The Centers for Disease Control and Prevention (CDC) estimate that 76 million people get sick, more than 325,000 are hospitalized, and 5,000 die as a result of foodborne illnesses each year. In addition to the health burden, the economic burden of foodborne disease is staggering, with an estimated loss of productivity ranging between $20 and $40 million per year and the cost of hospitalization estimated at $3 billion per year. When considering the most vulnerable populations, such as the elderly, the immunocompromised, and the very young, foodborne diseases like norovirus are significant (Mead et al., 1999).

According to Mead and co-authors (1999), norovirus accounts for an estimated 23 million cases per year in the U.S. and about 40% of these cases result from foodborne transmission. Of the estimated 23 million illnesses, 9.2 million are foodborne, representing 66.6% of total foodborne illnesses. The total estimated norovirus hospitalizations per year are 50,000, of which 20,000 are foodborne, representing 32.9% of total foodborne illnesses. The total number of estimated norovirus deaths per year is 310, of which 124 are foodborne, representing 6.9% of total foodborne illnesses.

Norovirus in School Settings

Few studies have been conducted in order to determine the burden of norovirus in school settings. Three Government Accountability Office (GAO) reports highlighted food safety as a growing concern in school settings (GAO, 2000; GAO, 2003; GAO, 2006). Daniels and co-authors (2002) examined outbreaks occurring in school settings from 1973 through 1997 and findings from that study indicate that 14 viral outbreaks were reported. Of those, Norwalk-like viruses accounted for five outbreaks, affecting a total of 804 persons and resulting in two hospitalizations. Findings from the Daniels and co-authors study indicated that bacterial pathogen outbreaks accounted for a greater proportion of outbreaks than those of viral etiology. Salmonella was identified in 36% of outbreak reports with a confirmed etiology.

The proportion of norovirus outbreaks of confirmed etiology nationwide increased from 1% in 1991 to 12% in 2000 (Widdowson, 2005). Development of more sensitive molecular diagnostic techniques over the last several years has allowed for a more accurate estimation of the burden of norovirus. School environments are increasingly becoming the most common settings for the occurrence of norovirus outbreaks, in large part because norovirus tends to thrive well in closed to semiclosed environments like schools (Lynch, Painter, Woodruff, & Braden, 2006).

The purpose of our descriptive retrospective study was to analyze data collected within the Electronic Foodborne Outbreak Reporting System (eFORS) in school settings in order to examine the magnitude of foodborne disease etiologies, particularly norovirus, and to recommend strategies for prevention.

Norovirus (genus Norovirus, family Caliciviridae) is an important foodborne illness because it is a major cause of acute gastroenteritis in schoolchildren and the cause of significant absenteeism in the U.S. Norovirus outbreaks are very difficult to contain due to the fact that the pathogen is highly contagious. Norovirus is transmitted through food, water, and person-to-person contact and only a small infectious dose (less than 100 viral particles) is required to cause infection. Viral shedding can occur over a prolonged period of time even without clinical symptoms. The pathogen is extremely persistent in the environment and resistant to disinfection via agents. The incubation period for norovirus is 12-48 hours and the infection can last from 12 to 60 hours. Onset of symptoms is acute and generally includes abdominal cramps, vomiting, watery nonbloody diarrhea, and at times mild fever. …