Noroviruses – Looking at the Evidence for What We Know and What We Do

Chong Wei Ong1,2

1Canberra Hospital and Health Services, PO Box 11, Woden, ACT 2606; chong-wei.ong@act.gov.au

2Calvary Public Hospital Bruce, PO Box 254, Jamison Centre, ACT 2614; chong-wei.ong@act.gov.au

 

Noroviruses are a leading cause of gastroenteritis worldwide, involving both sporadic cases and outbreaks. Infections are difficult to prevent and control, due to their low infectious dose, high shedding titre, and environmental stability. In the healthcare setting, person-to-person transmission has been implicated, via direct contact, aerosols, fomites and the environment.

Although there is much experience with the management of norovirus outbreaks, knowledge gaps still remain concerning viral shedding and transmission. The role of asymptomatically infected persons is not well defined. Recognition of chronic norovirus diarrhoea as an entity distinct from an acute, self-limiting illness also brings challenges. Uncertainties exist concerning laboratory diagnosis and result interpretation.

Despite the availability of guidelines for Infection Prevention and Control and Public Health interventions, there is a lack of high quality evidence for the effectiveness of some recommended control measures. Many studies claiming efficacy for interventions are observational, being single outbreak reports with no control arms. The impact of implementing isolation and transmission-based precautions has not been well-quantified. Ward or facility closures and temporary suspension of visitors are controversial in some settings. The optimal hand-hygiene method to reduce transmission is subject to debate. Variations also exist in environmental disinfection methods. Good evidence-based treatment options for infection are lacking.

This presentation reviews some of the evidence relating to noroviruses and outbreak management. It highlights some of the difficulties posed by the absence or inadequacy of evidence in some areas and the presence of conflicting evidence in others.