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Updated: Feb 1, 2026

Swab Sampling Method for the Detection of Human Norovirus on Surfaces
Published on: February 6, 2017
An outbreak of norovirus infection caused by ice cubes and a leaking air ventilation valve
K Jalava1, A Kauppinen2, H Al-Hello2
1Department of Food Hygiene and Environmental Health and Department of Mathematics and Statistics, University of Helsinki, Helsinki, Finland.
Abstract:
A gastrointestinal outbreak was reported among 154 diners who attended a Christmas buffet on the 9 and 10 December 2016. A retrospective cohort study was undertaken. Faecal samples, water, ice and an air ventilation device were tested for indicators and routine pathogens. Altogether 26% (24/91) fulfilled the case definition of having typical viral gastrointestinal symptoms. Norovirus genogroup I was detected in faecal samples from three cases. One of these cases tested positive also for sapovirus and had a family member testing positive for both norovirus and sapovirus. A diner who drank water or drinks with ice cubes (risk ratios (RR) 6.5, 95% confidence intervals (CI) 1.5-113.0) or both (RR 8.2, 95% CI 1.7-145.5) had an increased risk in a dose-response manner. Ice cubes from three vending machines had high levels of heterotrophic bacteria. A faulty air ventilation valve in the space where the ice cube machine was located was considered a likely cause of this outbreak. Leaking air ventilation valves may represent a neglected route of transmission in viral gastrointestinal outbreaks.
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