[Hospital outbreak of viral gastroenteritis attributed to Norwalk-like viruses in Japan].

Background: Norwalk-like viruses (NLVs), RNA viruses in the family of Caliciviridae, are known as a pathogen of nonbacterial food-borne gastroenteritis associated with eating raw oysters. NLV can spread from person to person with strong infectivity and can cause large epidemics in communities, schools, nursing homes, and hospitals. Here, we describe an outbreak of gastroenteritis associated with NLVs, possibly introduced from outside the hospital, in four different wards on four different occasions between November 1999 and April 2000, in a university affiliated hospital in Tokyo.

Method: Total 61 specimens (stool or vomitus) from 46 patients and staffs were collected. Reverse transcription-polymerase chain reaction (RT-PCR) test was performed on each specimen. Standard precautions were applied strictly as control.

Result: NLV was detected in 40 specimens from 28 patients and staff (20 patients, 8 nurses). Attack rate of the patients were 0.19, nurses were 0.15, and doctors were 0.07.

Conclusion: The spread of NLV from person to person is considered to be a major infection pathway in each ward. A nurse is at a high risk of infection as a patient in some wards. A stringent policy of control must be applied.