An outbreak of multiple norovirus strains on a cruise ship in China, 2014

Aims: To determine the cause of an outbreak of acute gastroenteritis that occurred on a cruise ship sailing along the Yangzi River from Chongqing to Nanjing, China. Methods and Results: Noroviruses were identified by reverse transcription-PCR (RT-PCR) in rectal swabs from 34 of 54 subjects tested (63.0%). Sequencing and genotyping showed that noroviruses of up to seven different genotypes circulated in this outbreak: noroviruses GI.1, GI.2, GI.3, GI.4, GI.8, GI.9 and an uncommon strain GII.17. Common genotypes were not identified in this event. None of the food or water samples were tested positive for noroviruses. Conclusions: We suspected that it was a point-source infection due to contaminated water or food harvested from contaminated water, taking account of the co-existence of diverse norovirus genotypes. Significance and Impact of the Study: In this study, we presented the molecular investigation of a norovirus outbreak on a cruise in China. We revealed that the outbreak was caused by several different norovirus genotypes and analysed the possible source of infection as well, thus facilitating the evaluation of epidemiological issues regarding noroviruses in this area.