Molecular Epidemiology of “Norwalk‐like Viruses” in Outbreaks of Gastroenteritis in the United States

TLDR

The study aimed to determine the importance of and characterize Norwalk‑like viruses (NLVs) in 90 outbreaks of nonbacterial gastroenteritis reported to 33 state health departments between January 1996 and June 1997. Fecal specimens from these outbreaks were examined using reverse transcription‑polymerase chain reaction and nucleotide sequencing. Reverse transcription‑polymerase chain reaction detected NLVs in 86 of 90 (96%) outbreaks, with the majority occurring in nursing homes and hospitals and most transmissions linked to contaminated food; nucleotide sequencing revealed high strain diversity but also a predominant strain, demonstrating that most nonbacterial gastroenteritis outbreaks in the United States are associated with NLVs and that sequence analysis is a robust tool for outbreak linkage and differentiation.

Abstract

Fecal specimens from 90 outbreaks of nonbacterial gastroenteritis reported to 33 state health departments from January 1996 to June 1997 were examined to determine the importance of and to characterize "Norwalk-like viruses" (NLVs) in these outbreaks. NLVs were detected by reverse transcription-polymerase chain reaction in specimens from 86 (96%) of 90 outbreaks. Outbreaks were most frequent in nursing homes and hospitals (43%), followed by restaurants or events with catered meals (26%); consumption of contaminated food was the most commonly identified mode of transmission (37%). Nucleotide sequence analysis showed great diversity between strains but also provided evidence indicating the emergence of a common, predominant strain. The application of improved molecular techniques to detect NLVs demonstrates that most outbreaks of nonbacterial gastroenteritis in the United States appear to be associated with these viruses and that sequence analysis is a robust tool to help link or differentiate these outbreaks.