A norovirus outbreak associated with environmental contamination at a hotel

In December 2006, an outbreak of gastroenteritis occurred involving 372 guests and 72 employees at a hotel after a guest vomited in corridors on the third (F3) and 25th (F25) floors. Norovirus with identical genotype was confirmed by real-time reverse transcription-polymerase chain reaction in faecal samples from guest cases and employees. Spread of the outbreak on F25 was compared with that on F3. The attack rate in the guests who visited F25 alone (15.0%, 106/708 guests) was significantly higher than in those who visited F3 alone (3.5%, 163/4710 guests) (relative risk 4.3, 95% confidence interval 3.4-5.5, P<0.001). The outbreak on F3 ended within 2 days, while that on F25 extended over 7 days. The environmental ratios of F3 to F25 were 7.4 for volume, 6.9 for floor area and 7.6 for ventilation rate. This outbreak suggests that environmental differences can affect the propagation and persistence of a norovirus outbreak following environmental contamination.