To the Editor: Noroviruses are an important cause of acute gastroen-teritis, and outbreaks caused by these viruses have emerged as a major chal-lenge to the healthcare, leisure, and tourism industries. The primary reason is their highly effi cient transmission among persons in semiclosed popula-tions such as those in healthcare facili-ties, hotels, and cruise ships. During an outbreak, primary cases result from exposure to a fecally contaminated vehicle (e.g., food or water), whereas secondary and tertiary cases among contacts of primary case-patients re-sult from person-to-person transmis-sion (1). Airborne and fomite trans-mission also play a role in the virus spread during outbreaks (2). Trans-mission through recreational water has also been described (3).
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