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To better understand factors associated with confirming the etiologic organism and identifying the food vehicle responsible for foodborne-disease outbreaks, we examined data from outbreaks reported in 1998 and 1999 through active surveillance by Foodborne Disease Active Surveillance Network (FoodNet) surveillance areas in 7 states. In 71% of these outbreaks, no confirmed etiology was identified, and in 46%, no suspected food vehicle was identified. Outbreaks involving > or =10 cases were significantly more likely to have their etiology identified than were smaller outbreaks. In two-thirds of outbreaks in which an etiology was not confirmed, no stool specimens were collected for laboratory testing; in 55% of these outbreaks, neither clinical specimens nor food samples were tested. If the etiology of and factors contributing to foodborne-disease outbreaks are to be understood, adequate resources must be available to allow specimens to be collected and tested and epidemiologic investigations to be conducted appropriately.

This investigation evaluated the role of Norwalk-like virus (NLV) and other viruses (rotavirus, enteric adenovirus, and enterovirus) in 11 outbreaks of acute nonbacterial gastroenteritis that occurred in multiple settings in a span of 18 months in New York State. To determine the etiology of illness, patients' stool specimens were analyzed with a combination of reverse-transcription polymerase chain reaction (RT-PCR) and nucleotide sequencing, cell culture, and ELISA diagnostic techniques. NLV was detected from all of these outbreaks, with an overall detection rate of 64% (51 of 79) for all specimens tested. Repeated attempts to isolate other viral pathogens were unsuccessful. Phylogenetic analysis of a subset of 27 specimens from these outbreaks showed the presence of both genogroup I and genogroup II NLVs. A spectrum of different nucleotide sequences were detected, demonstrating interoutbreak sequence variation and unrelated infections. NLV is a significant causative agent of diarrhea outbreaks in New York State.

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