Upper Respiratory Tract Infection Trends in a Psychiatric Institute in Singapore

Objectives: To compare the incidence of upper respiratory tract infection (URTI) between inpatients at the Institute of Mental Health in Singapore and the general population over 8 years to determine the effectiveness of our infection control strategies.

Methods: Data for cases of influenza and URTI at our institute between January 2012 and December 2019 were collected. National data were derived from weekly infectious disease bulletins that report daily averages of people attending polyclinics/surgeries with influenza and URTI. Interrupted time series analyses were used to determine the impact of infection prevention and control strategies on incidence.

Results: Over the 8 years, there were 1607 cases of URTI involving 182 clusters, equal to 3.16 cases per 10 000 patient-bed-days. 965 (60%) cases and 95 (52%) clusters occurred in long-stay wards, whereas 642 (40%) cases and 87 (48%) clusters occurred in acute wards. The median cluster size was 12 in the long-stay wards and 7 in the acute wards (p < 0.0001). The spikes in cases in June and December may be attributed to the increased staff and visitor mobility during school vacations in June and December. Strategies implemented during the study period did not significantly reduce the incidence of URTI. Previous strategies implemented in 2005 to meet accreditation standards are more likely to be contributors.

Conclusion: Infection control strategies of our institute appear to be effective, because the incidence of URTI was lower in our institute than in the community. The similar incidence of URTI in acute and long-stay wards indicates that service-user turnover is not a contributor. Rather, staff and visitors are more likely to be the vector. The larger clusters in long-stay wards indicates a greater risk of transmission in such settings. Increased activity in our institute during school vacations may be associated with an increase in cases in June and December. It is difficult to determine if strategies implemented during the study period successfully reduce the incidence of URTI.