Involvement of workers in closed and semiclosed institutions in outbreaks of acute gastroenteritis due to norovirus

Abstract

Norovirus outbreaks frequently occur in closed or semiclosed institutions. Recent studiesin Catalonia and various countries indicate that, during outbreaks in these institutions, norovirus isdetected in between 23% and 60% of workers, and the prevalence of infection in asymptomatic workersinvolved in outbreaks ranges from 17% to 40%. In this work, we carried out a prospective studyto investigate the involvement of workers in closed and semiclosed institutions during outbreaks.The attack rates (ARs) and the rate ratios (RRs) were calculated according to the type of transmissionand occupational category. The RRs and 95% confidence intervals (CIs) between workers and userswere calculated. The mean cycle of quantification (Cq) values were compared according to thegenogroup and the presence of symptoms. ARs were higher in person-to-person transmission thanin common vehicle outbreaks, and 38.8% of workers were symptomatic. The RR between workersand users was 0.46 (95% CI 0.41-0.52). The ARs in workers were high, particularly in workers withcloser contact with users. The mean Cq was lower in patients than in asymptomatic infected persons,although the difference was only significant for genogroup I (GI). The frequency of asymptomaticinfected persons suggests that personal hygiene measures should be followed by all workers in thecenters affected.