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Randomised controlled study shows that deployment of germicidal ultraviolet technology results in a significant reduction in the cumulative incidence in respiratory viral infections.
For those living in long-term residential aged care, common respiratory viral infections are a major cause of hospitalisation and death. This reflects both the increased vulnerability associated with advanced age and the ease within which pathogens can spread within aged care environments. With the Australian population ageing rapidly, and novel respiratory pathogens, such as SARS-CoV-2, predicted to emerge ever more frequently, the need to identify effective ways to reduce pathogen transmission within aged care settings is urgent.
Our current inability to contain outbreaks of respiratory viral infections in aged care settings was clearly evident during the COVID-19 pandemic. Australians aged over 65 accounted for around 95% of deaths. Outbreaks in residential aged care settings, where infection risk is heightened due to communal living arrangements and underlying health conditions, commonly reported mortality rates above 30%. That such devastating outbreaks occurred despite concerted infection control efforts highlighted the need for a re-examination of the strategies employed to protect vulnerable older adults from respiratory infections.
A particular challenge in identifying such strategies is the need to address all major modes of respiratory virus transmission. Current infection control measures, such as the use of facemasks or physical distancing, are principally designed to prevent transmission by cough droplets, which are relatively large and settle onto surfaces relatively rapidly. In contrast, airborne transmission, involving infective aerosols that remain suspended in the air column for much longer periods, remains largely unaddressed, despite evidence of the importance of this this mode of transmission within the built environment.
Germicidal ultraviolet light technology
One approach to preventing airborne transmission of respiratory viruses is through the use of germicidal ultraviolet (GUV) light technology. Such technology can render viruses suspended within the air column non-infectious by damaging their nucleic acids, and has been shown to be effective within laboratory settings for a wide range of common respiratory viruses. However, evidence that such technology can protect vulnerable populations, such as those in residential aged care, is currently lacking.
We undertook a two-year randomised cluster-controlled clinical trial to determine whether deployment of germicidal ultraviolet (GUV) light technology in residential aged care settings in South Australia is effective in reducing the rates of symptomatic respiratory infections. To minimise disruption to residents, commercially available GUV appliances were installed only within communal areas, such as dining rooms, corridors, lift lobbies, and lounges. A crossover design was employed, whereby zones within facilities were paired and randomly assigned to begin the intervention period in an “active” (appliances switched on continuously) or “inactive” (appliances switched off continuously) phase. After a six-week intervention period and a two-week washout (all appliances switched off), zones underwent crossover to the alternate intervention phase. The use of such an approach allowed us to make direct comparisons of infection rates between intervention and control, regardless of evolving infection control measures or shifts in viral exposures. This study schedule was repeated seven times over two years, including during multiple viral outbreaks, and cases of acute respiratory infection were identified based both on symptomatic presentations and pathology testing.
While our primary outcome — rates of respiratory infection during individual intervention periods — did not show GUV to provide a statistically significant reduction compared to control (likely reflecting the relatively low case incidence), the cumulative incidence of infections over the study period did. The number of infections during active intervention periods was 12.2% lower compared to control, a reduction estimated to equate to more than 90 fewer cases per 1 000 residents each year.
This finding was particularly heartening, given that the study was designed and undertaken during the challenging and rapidly evolving circumstances of the COVID-19 pandemic, including limited access to aged care facilities and pathology testing services, rapidly changing infection control mandates, and funding constraints. Despite this, we were able to demonstrate significant benefit across diverse real-world aged care settings.
The potential to save lives
The COVID-19 pandemic starkly illustrated the devastating impact of rapid respiratory virus transmission within residential aged care settings. While outbreaks of seasonal respiratory infections are often regarded as inevitable in these environments — given the close co-housing of individuals with heightened vulnerability — there is increasing recognition that such events are not unavoidable. As the number of Australians residing in aged care continues to grow, so too does the imperative to identify more effective strategies to mitigate this preventable burden of disease.
Our study aimed to evaluate the effectiveness of a technology that, although supported by substantial laboratory evidence, has not been widely assessed in real-world aged care environments. Despite GUV appliances being installed only in selected shared areas, the observed reduction in cumulative acute respiratory infection cases was considerable. Extrapolated to the approximately 250 000 Australians currently living in long-term aged care, these findings suggest the potential to prevent around 23 000 cases, 2 300 hospitalisations, and 90 deaths each year. Such reductions would not only lessen the direct health impact on residents but also alleviate broader pressures on the healthcare system.
While our findings are encouraging, further research is needed to confirm these benefits and to optimise implementation. Future studies should explore deployment strategies that maximise effectiveness, alongside comprehensive cost–benefit analyses incorporating factors such as staff absenteeism and operating costs. Additional work should also examine potential benefits for residents at increased risk, including those with chronic respiratory conditions or advanced dementia.
Finally, it is essential to acknowledge that no single intervention can prevent respiratory infections in aged care. Effective infection control requires a multifaceted approach. GUV technology should therefore be viewed as a complementary measure — enhancing, rather than replacing, established practices such as surface hygiene, social distancing, and vaccination.
Dr Andrew Shoubridge is a Postdoctoral Research Fellow in the Microbiome and Host Health Programme at the South Australian Health and Medical Research Institute (SAHMRI), and Flinders Health and Medical Research Institute (FHMRI) at Flinders University.
Professor Geraint Rogers is the Director of the Microbiome and Host Health Programme at SAHMRI, and Matthew Flinders Professor of Infection and Immunity Programme in FHMRI at Flinders University.
The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated.
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