Foodborne disease outbreaks declined with new reporting system

CDC. MMWR. 2013;62;41-47.

  • February 1, 2013

The number of foodborne disease outbreaks reported in 2009 and 2010 declined 32% compared with the mean from the past 5 years, according to a recent Morbidity and Mortality Weekly Report.

During 2009-2010, 1,527 foodborne disease outbreaks were reported (675 in 2009). The outbreaks resulted in 29,444 cases of illness, 1,184 hospitalizations and 23 deaths.

The most significant decline in outbreak reporting was observed among norovirus outbreaks, although norovirus remained the most common cause of outbreaks and illness (42%). This decline may have been a result of the National Outbreak Reporting System (NORS), a new reporting form and online data entry interface developed in 2009. NORS might have led to more appropriate classification of outbreaks previously reported as foodborne, resulting in fewer reports of foodborne norovirus outbreaks.

Salmonella was the second most common cause of reported outbreaks and illness. Salmonella caused 30% of the single-etiology outbreaks and 36% of illnesses. Of the outbreak-related illnesses, 4% resulted in hospitalization, with three main causes being Salmonella (49%), Shiga toxin-producing Escherichia coli (STEC; 16%) and norovirus (9%).

Food was reported for 43% of outbreaks, and 46% of those could be assigned to one of 17 predefined commodities. The most commonly implicated were beef (13%), dairy and fish (13% each), and poultry (11%).

The commodities with the most outbreak-related illnesses were eggs (2,231 illnesses), beef (928), poultry (826).

NORS receives reports of outbreaks of enteric disease transmitted through water, person-to-person contact, contact with animals, environmental contamination and indeterminate means, as well as through food.

A single confirmed or suspected etiologic agent was indentified in 1,022 (67%) outbreaks, 790 of which were confirmed. Among the confirmed outbreaks 52% were caused by bacteria; 42% by viruses; 5% by chemicals and toxins; and 0.2% by parasites.

Researchers said the findings are subject to at least four limitations. First, only a small proportion of foodborne illnesses reported each year are identified as associated with outbreaks. Second, many outbreaks had an unknown etiology, food vehicle or both, and conclusions drawn from outbreaks with a confirmed of suspected etiology or food vehicle might not apply to outbreaks with unknowns. Third, CDC’s outbreak surveillance system is dynamic; agencies can submit new reports and can change or delete previous reports as new information becomes available. Last, because of changes in the surveillance system implemented in 2009, comparisons with preceding years should be made with caution.

Disclosure: The researchers report no relevant financial disclosures.

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