An outbreak of norovirus gastroenteritis in an Austrian hospital, winter 2006-2007

BACKGROUND: Norovirus is easily spread from person to person by the fecal-oral route and through aerosols or by vehicles such as contaminated food or water. The virus is able to survive in the environment for many days, which enables outbreaks to be prolonged. We describe a norovirus outbreak and its control measures in an Austrian secondary-level hospital during December 2006 - February 2007. METHODS: A descriptive-epidemiological investigation of the outbreak was undertaken. We also determined outbreak costs, including the estimated lost revenue associated with department closures and the cost of sick leave and cleaning expenses. Selected stool specimens were tested for norovirus RNA. RESULTS: In the hospital, 90 persons with symptoms and signs consistent with norovirus gastroenteritis with clinical onset between December 1, 2006 and February 13, 2007 were identified. Out of these, 56 patients and 14 persons among the hospital staff fulfilled the definition of an outbreak case (77.8%), and 20 cases (22.2%) were identified as non-outbreak cases including 13 community-acquired cases of norovirus gastroenteritis and 7 clinical-suspected cases of norovirus gastroenteritis associated with health care facilities other than the affected hospital. The Department of Internal Medicine was the mainly affected department (46 patient-cases and 6 staff-cases). Considering hospital patients, who have been hospitalised between December 1, 2006 and February 13, 2007 as cohort at risk of nosocomial norovirus infection, the nosocomial hospital outbreak attack-rate was 5.9% (56/947). A total of 120 hospital staff members worked in the period from December 1 to February 13, which makes an attack-rate among the hospital staff of 11.7% (14/120). Norovirus strain GII.4 variant 2006b was detected, which has been circulating widely in Europe since 2006. The total cost of the outbreak for the Department of Internal Medicine was a,not sign 80,138. CONCLUSIONS: The significant disruption of patient care and the cost of this single nosocomial outbreak support strict implementations of adequate and timely control measures based on evidence-based recommendations.