Norovirus in residential care facilities: does prompt notification of outbreaks help?

Outbreaks of viral gastroenteritis occur regularly in residential care facilities (RCFs), with norovirus being the most common agent. Notification of outbreaks to public health authorities is encouraged in Australia, although there is limited evidence that this results in public health benefit. The aim of this study was to investigate if prompt notification of suspected norovirus outbreaks to public health authorities is associated with a reduction in either the duration or attack rate of outbreaks. Viral gastroenteritis outbreaks notified from Queensland RCFs between 2004 and 2007 were analysed. Foodborne outbreaks were excluded, along with 6 outbreaks where viruses other than norovirus were identified as the causative agent. Of the 264 remaining outbreaks, 70.8% were laboratory-confirmed as being due to norovirus. The average time to notification was 4 days and the average duration of outbreaks was 12 days. Outbreaks notified promptly (within 1 day) were of significantly shorter duration compared with outbreaks notified within 2-3 days (P < 0.02) or 4 or more days (P < 0.001). Early notification of outbreaks was not significantly associated with a reduced attack rate, however there was a significantly higher attack rate in facilities with less than 150 individuals at risk compared with facilities with 150 or more individuals at risk (30% versus 18%, respectively; P < 0.001). The shorter duration of promptly notified outbreaks provides some evidence to support recommendations from best practice guidelines for prompt notification of outbreaks by RCFs. However, further research is needed to unravel the interplay of factors that may influence the severity of viral gastroenteritis outbreaks in RCFs.