Norwalk virus gastroenteritis following raw oyster consumption

Area of Science:

• Gastroenterology
• Public Health
• Foodborne Illness

Background:

• Norwalk virus causes acute gastroenteritis, often mistaken for
• stomach flu.
• Oysters are a potential vehicle for transmitting enteric viruses.
• Current monitoring of oyster waters relies on fecal coliform levels, which may not fully indicate viral contamination.

Purpose of the Study:

• To identify the causative agent of a gastroenteritis outbreak linked to raw oyster consumption.
• To investigate the epidemiology of the outbreak.
• To assess the adequacy of current water quality monitoring for detecting enteric virus contamination.

Main Methods:

• Case-finding among party attendees.
• Clinical symptom assessment.
• Serologic radioimmunoassay for Norwalk virus identification.
• Analysis of oyster batch for fecal coliform levels.

Main Results:

• Six of 13 attendees developed gastroenteritis after eating raw oysters.
• Nausea, vomiting, and diarrhea were the primary symptoms.
• Norwalk virus was confirmed via radioimmunoassay.
• Incriminated oysters exceeded fecal coliform standards.

Conclusions:

• Raw oyster consumption was linked to a Norwalk virus outbreak.
• Fecal coliform levels showed a weak correlation with enteric virus presence in oysters.
• Further research is required to improve monitoring of shellfish harvesting waters for viral pathogens.