Infection control measures for norovirus: a systematic review of outbreaks in semi-enclosed settings

We carried out a review of published, peer-reviewed articles to assess the evidence for effectiveness of control measures during norovirus outbreaks in enclosed settings. There were 47 papers identified for review, some of which reported more than one outbreak, providing 72 outbreaks for analysis. We extracted the following data items: attack rates; the number of people affected and at risk, case or outbreak definition; whether outbreak control measures were implemented; and claims of effectiveness of interventions. We analysed the data to identify any differences in the outbreaks experienced in different settings and any differences experienced during outbreaks according to whether control measures were implemented or not. All of the reviewed papers described outbreaks occurring in industrialised countries. We found no evidence that implementing infection control measures affected the duration of outbreaks, or the attack rates either overall (all settings combined) or within particular settings. The median outbreak duration was 16 days (range: 1-44) compared with 14 (range: 2-92) where control measures were and were not utilized, respectively. Sound infection control procedures are key to controlling norovirus outbreaks but unfortunately, the present body of the published literature does not provide an evidence-base for the value of specific measures.