SUMMARY: An outbreak of norovirus GII.4/Sydney_2012 affected a China elder care facility in December 2012. A total of 39 elderly people and staff met the outbreak case definition. The attack rates in the elderly and the staff were 15.9z (31/195) and 23.2z (19/82), respectively, including 13 asymptomatic cases in the staff. The result of gene sequencing revealed that the outbreak was caused by norovirus GII.4 Sydney. The mode of transmission of this outbreak was proven to be person-to-person. The first case (a self-cared elder) was affected outside the elder care facility and was not isolated after returning. Norovirus was transmitted via close contact among the self-cared elderly. Then, through servicerelated close contact, the attendants promoted the cross-transmission between the self-cared elderly and the nursed elderly. The virus was also spread among the staff via daily contact. In the elder care facility, the asymptomatic cases in the attendants played an important role in the transmission of norovirus, which deserves high attention.

Noroviruses (NoVs) cause gastroenteritis in all age groups. To investigate an acute gastroenteritis outbreak in Shenzhen, South China, we analyzed the presence of NoVs in fecal specimens and drinking water samples. Viral RNAs were extracted from fecal suspensions and water concentrates made by membrane adsorption-elution, and NoV was detected by reverse transcription-polymerase chain reaction (RT-PCR). Among the 43 diseased workers at the two factories and one construction site, NoVs were detected in 19 out of 28 stool specimens (68%) and 3 out of 16 water samples (19%). Importantly, the six NoV strains identified from the water and the stool samples share over 99% sequence identity and all belong to GII 4 viruses. Epidemiological survey also identified a water pipe breakage possibly causing the water contamination, and confirmed that the contaminated drinking water largely contributed to the NoV gastroenteritis outbreak. To our knowledge, this is the first time that a viral concentration and detection method for waterborne NoV is applied to a gastroenteritis outbreak in China.