It’s the most Chunderful time of the year (or maybe not). The Norovirus ‘season’ will still be on us and a few points are well worth reflecting on. A recent systematic review of Norovirus risk in high and middle-income countries asserts that there may be as many as 12.5 million infections annually these countries alone, with possibly as many as 2.2 million outpatient visits related to the illness. Personally I have always liked having a bit of norovirus around. Keeps the staff on their toes and gives a good indicator of how IPC is really being performed rather than another set of 99% compliant hand hygiene audits.
So, a significant burden on healthcare with outbreaks relatively common when ‘there’s a lot of it about’. Seeking to WINCL (Where Is Norovirus Control Lost?) out the root cause of outbreaks, the Infection Prevention Society research and development group led by Evonne Curran (AKA @EvonneTCurran) undertook a mixed-methods, multi-centre, prospective, enhanced surveillance study to determine whether the source of an outbreak could be determined. A total of 53 centres took part and 537 outbreaks were examined, the authors noting that the study took part during a ‘quiet season’. In 79% of outbreaks the index case was identified, however residential care facilities did better at this than acute care facilities, which, as the authors point out, have a far faster client turnover. The much-maligned ‘visitor’ sometimes used as a ‘get out of jail free card’ by hospital spokespersons was deemed to be the index case in only 3% of outbreaks (although 70% of these had symptoms before visiting). Interestingly, only 12% of index cases were symptomatic on admission and worryingly only 25% of those that were admitted with symptoms were correctly isolated immediately. Most worryingly is the fact that ‘Presenteeism’ appears to be an issue, already the subject of a blog from our good friends in the ‘Controversies‘ blog across the pond. 69% of healthcare workers who were deemed to be index cases experiencing symptoms before coming to work. Could this be a result of overzealous Human Resource departments’ scrutiny of staff sickness?
The bottom line of this very useful study was that a significant number of ‘index cases’ had been admitted whilst asymptomatic and had exceeded the incubation period before becoming ill, meaning that there is significant misclassification of index cases and demonstrating the difficulty in getting to the ‘bottom’ of an outbreak. Overall, four themes emerged: diagnosis and therefore opportunities for isolation were missed, care services were under pressure (likely to increase), there were delays in implementing outbreak control measures and patient/resident location and proximity, where the wandering symptomatic patient wreaked havoc in their wake.
Just to possibly complicate matters, a recent study has indicated that 47% of cases shed virus for 21 days and that 11% of asymptomatic unexposed control patients tested positive for Norovirus. At what stage does a person become ‘non-infectious?’ The jury is still out as far as I can see although the Institute of Hospital Bed Managers somethimes wish this was measured in minutes rather than days.
Norovirus control is possible. Many organisations have good records and low staff attack rates although this is dependent on Vigilance, Observance of best practice, Messaging, Isolation and Testing (aka VOMIT).
Norovirus control is possible. Many organisations have good records and low staff attack rates although this is dependent on Vigilance, Observance of best practice, Messaging, Isolation and Testing (VOMIT). The thing is, ICPs always know which wards/floors are going to be a problem. I’d love to see how this intuition could be harnessed. Maybe a study in which IPC Teams are asked to predict where norovirus outbreaks may occur before the season in a sealed envelope and then do a post-season review. It would be very interesting to see how accurate the predictions are. My hunch is pretty good.