To the Editor: Norovirus, previously known as the Norwalk agent, is a recognised cause of acute diarrhoeal illness in all age groups, but its significance in hospitalised children is poorly described. Noroviruses cause infection worldwide and year-round, with a distinct increase in disease occurrence in colder months.1

Rotavirus has long been recognised as the most important viral cause of gastroenteritis in young children, causing significant morbidity, as well as cost to the community of hospital admission and lost parental productivity.2 In July 2007, two new rotavirus vaccines were licensed for use in Australian infants; their use has reduced severe rotavirus disease requiring hospital admission.3 One difficulty in accurately documenting the role of norovirus in childhood acute diarrhoeal illness has been the limited availability of routine diagnostic testing. Enzyme-linked immunosorbent assay (ELISA) for noroviruses is now available commercially; it has limited sensitivity of 55%–93% but good specificity of 73%–97%.

We retrospectively reviewed the frequency of detection of norovirus in the faecal samples taken from inpatients and outpatients with acute gastroenteritis at a tertiary paediatric hospital. We tested stool samples of 3962 children with episodes of acute diarrhoeal illness in a 12-month period (2007) and detected norovirus in 122 (3.1%). Ninety-one of the children infected with norovirus were admitted to hospital; 63 patients had a stay of less than 7 days with a median of 1 day, while 28 patients where in hospital for more than 7 days. The norovirus infection in 30 of the inpatients (33%) was hospital-acquired. Most hospital-acquired infections occurred in patients hospitalised for more than 7 days (19 of 28; 68%), and most of these patients had predisposing medical conditions, predominantly immunosuppression due to treatment for malignancy or other causes.

Norovirus is a significant cause of viral gastroenteritis in infants and children. Our findings are comparable with those of other studies, which indicate that norovirus infection causes 20%–88% of viral gastroenteritis in children and is responsible for a significant proportion of hospital admissions of children with gastroenteritis.4,5 With the introduction of universal rotavirus vaccination for Australian infants, the importance of norovirus as a cause of gastroenteritis in infants and children is likely to increase. We recommend that hospitals which admit children consider using norovirus testing to establish the incidence and prevalence of disease, and to inform public health authorities responsible for infection control policy and practices.