Risk Factors for Norovirus in the Institutionalized Elderly

Most of the institutional outbreaks of norovirus in Hong Kong occur in elderly homes, the proportion being 69 percent in 2006. Residents in elderly homes are a special population seriously affected by norovirus infections, it is necessary to investigate the risk factors of the norovirus outbreaks in Hong Kong elderly homes at the facility level.

Hualiang Lin, of the School of Public Health and Primary Care at the Chinese University of Hong Kong, and colleagues, report on their study in which a cohort of 748 elderly homes was followed up from January 2005 to December 2007; each elderly home was treated as one observation unit and the outcome event was the norovirus outbreak. Cox regression models were fitted to estimate the rate ratio (RR) and 95% confidence interval (CI) for the potential risk factors.

The researchers report that a total of 276 norovirus outbreaks were confirmed during the study period; the outbreak rate was 12.2 (95% CI: 9.9-14.6) per 100 home-years; elderly homes with a larger capacity (RR=1.4, 95% CI: 1.3-1.5 (per 30-resident increment)), a higher staff-to-resident ratio (RR=1.2, 95% CI: 1.1-1.3 (per 1/30 increment) and better wheelchair accessibility (RR=2.0, 95% CI: 1.3-3.2) were found to have an elevated norovirus outbreak rate in Hong Kong elderly homes; Elderly homes with partitions between beds had a lower rate of norovirus outbreaks (RR=0.6, 95% CI: 0.4-0.8).

Lin, et al. conclude that elderly home capacity, staff-to-resident ratio and wheelchair accessibility were risk factors for norovirus outbreaks in Hong Kong elderly homes. Partitions between beds were a protective factor of norovirus outbreaks. They add that these results should be considered in the infection control in Hong Kong elderly homes. Their reearch was published in BMC Public Health.

Reference: Lin H, Ng S, Chan S, Chan WM, Lee KCK, Ho SC and Tian L. Institutional risk factors for norovirus outbreaks in Hong Kong elderly homes: a retrospective cohort study. BMC Public Health 2011, 11:297doi:10.1186/1471-2458-11-297