Norovirus disease associated with excess mortality and use of statins: a retrospective cohort study of an outbreak following a pilgrimage to Lourdes

Although norovirus infection is generally known to be a mild disease, there is some evidence for severe outcome. An outbreak in a Dutch psychiatric institution, originating from pilgrims returning from Lourdes (France), provided an opportunity for performing a retrospective cohort study in order to identify risk factors for norovirus disease and excess mortality. Relative risks (RR) including 95% confidence intervals (CI) showed that attending the pilgrimage (RR 2.0, 95% CI 1-4-3.0) and age >70 (RR 17,95% CI 1.2-2.2) were risk factors for symptomatic infection. In a subset of patients, for whom more detailed information was available, the use of statins was associated with norovirus disease when adjusted for underlying condition (adjusted odds ratio 3.9, 95% CI 1.2-13.0). Mortality was higher in cases infected during the pilgrimage compared to other residents (RR 20.9, 95% CI 4.7-93.8). Norovirus disease can lead to severe outcome. The newly identified risk of statins for contracting norovirus disease may have considerable consequences for the Western world and needs prospective confirmation.