The role of dependency in a norovirus outbreak in a nursing home

The objectives of the epidemiological investigation were to describe factors associated with prolonged transmission of acute gastroenteritis in a nursing home during a norovirus outbreak.

A retrospective cohort study was conducted among residents (N = 89) and staff members (N = 86) of the nursing home. Outbreak description was performed in both residents and staff members. Among residents, attack rates and relative risks and their 95% confidence interval (95% CI) associated with different identified risk factors including consumption of normal, mixed and choped meal, score of dependency were calculated. A multivariate logistic regression model was fitted to assess the independent association between risk factors and the occurrence of acute gastroenteritis over the entire outbreak duration. Environmental investigations and review of practices were carried out among staff.

Respectively 49/89 respondent residents (AR 58%) and 9/47 respondent staff members (AR 19%) reported gastrointestinal symptoms between September 17 and October 21, 2016. Norovirus type II was isolated in five stool samples. Residents with dependency score (Gir) below 4 were at higher risk of acute gastroenteritis [RR 2.1 (95% CI 1.1-4.1)] compared to those autonomous. It was the only identified risk factor. In addition, the review of practices in staff identified several breaks in the application of hygiene control standards including misuse of personal protective equipment (gloves were not changed between caring for different patients), inappropriate hand hygiene technique, and disinfection of environmental surfaces with an ineffective product on norovirus.

This episode reminds the importance of early recognition of acute gastroenteritis cases and the implementation of rigorous management measures in order to limit the spread of the epidemic in a highly vulnerable dependent population.