Norovirus infections in a tertiary care centre - individual cases do not necessarily lead to an outbreak.

BACKGROUND: Norovirus is responsible for the majority of gastroenteritis outbreaks within healthcare settings. Routes of spread include foodborne-, waterborne- and especially person-to-person transmissions.

OBJECTIVE: We investigated the overall attack rate of norovirus, within and outside outbreak situations, transmitted via patient-to-patient contact in a tertiary care centre from January 2012 to March 2015.

STUDY DESIGN: We monitored exposed asymptomatic patients next to infectious patients for the development of symptoms of acute gastroenteritis following exposure.

RESULTS: We detected 102 patients with contact to 94 infectious patients. Of these only 11 patients developed typical norovirus symptoms after exposure while 91 patients remained asymptomatic. Total secondary attack rate was only 10.8%.

CONCLUSIONS: Patient-to-patient transmission of norovirus is potentially overestimated within clinical settings. Future prevention strategies should consider personal risk factors of exposed patients.