Epidemiology and impact of norovirus outbreaks in Norwegian healthcare institutions, 2005-2018.

AIM: The aim of this study was, for the first time, to describe in detail the epidemiology and impact of norovirus outbreaks in healthcare institituions (HCIs) in Norway to identify areas which may improve outbreak response.

METHODS: An analysis of all reported norovirus outbreaks in hospitals and long-term-care facilities (LTCFs) was carried out from week 34, 2005 to week 33, 2018. Seasonality, symptoms and number of cases among personnel and patients were described.

FINDINGS: A total of 20,544 cases, including 7044 healthcare personnel were reported in 965 outbreaks; 740 from LTCFs and 225 from hospitals. Median number of cases per outbreak was 15, interquartile range (IQR) 8-25 in LTCF; and 17, IQR 10-28 in hospitals. All regions reported outbreaks, with one-third of the municipalities having at least one outbreak in LTCFs during the study period. The start of the outbreak season happened almost four weeks earlier in hospitals than in LTCFs. The estimated average number of working days lost for healthcare personnel per year ranged from 1590 to 1944.

CONCLUSIONS: Norovirus outbreaks in Norwegian HCIs appears to have a substantial impact on both hospital and LTCFs all over Norway, especially during the winter months. That up to half of all cases were healthcare professionals emphasizes a need for further focus on infection control. Our results suggest that hospitals, affected first, could alert LTCFs in the area in order to prevent further outbreaks.