Hidden Systems: The Transmission of Infection in Healthcare Facilities

Clive Beggs PhD, FIMechE, FSB, FRSM
Professor of Medical Engineering, University of Bradford, UK



One feature of many infectious diseases is that in order for transmission to occur, individuals must come together in close proximity to each other. Consequently, the spread of infection can readily occur in buildings and in passenger transport vehicles, where individuals may spend many hours sharing the same enclosed space. The ease with which infections can spread in hospitals clearly demonstrates this. Yet our understanding of the role that the built environment plays in the transmission of infection is poor.

Infections are systems, whose behaviour is influenced by many complex factors. Yet all too often this fundamental fact is not fully appreciated. Too often microbiologists confuse knowledge of a particular pathogen gained in the laboratory, with the dynamics of any infectious outbreak that might be caused by that pathogen – the two are very different. In any outbreak of infection, the causative agent, the microorganism, is only one component amongst many that will influence how many individuals eventually become infected. Failure to recognise this, has resulted in a gross imbalance in the research undertaken in the field. While much work has been carried out into the gene expression of microorganisms, relatively little translational research has been undertaken to understand the dynamics of infectious systems. As a result, the epidemiology of many infections is poorly understood. This is particularly the case with hospital-acquired infections (HAIs), which are a major problem in healthcare facilities around the world. This lack of understanding is well illustrated by the experience of the UK in recent years. In hospitals, it is generally accepted that infections caused by MRSA and Clostridium difficile are predominantly spread by the handborne route. Consequently, prior to 2007, infection control clinicians in the UK focuses all their attention on increasing hand hygiene compliance. Unfortunately, while this policy was in place, infections caused by MSRA and C. difficile in the UK rose steadily, year on year [1, 2]. When the focus of this policy was switched, in about 2007, to include other measures such as: the deep cleaning of wards; the introduction of care bundles; the introduction of patient cohorting; and the screening of patients; MRSA and C. difficile infection rates fell by >50% [3]. Collectively, this suggests that our previous understanding of the epidemiology of MRSA and C. difficile infections was deeply flawed. Clearly, factors other than purely handborne transmission are at work and when these were addressed, so infection rates started to tumble.

One major feature of the UK hospital experience is that the reduction in HAIs coincided with a renewed emphasis on hospital cleaning and the introduction of deep cleaning of hospital wards. This raises intriguing questions as to the role that the clinical environment might play in the spread of HAI. Previously thought to be of little importance compared with hand-borne carriage, the clinical environment has been shown to be a major reservoir for nosocomial pathogens [4]. In addition, it has been shown that aerial dissemination resulting in surface contamination can play an influential role in the transmission of some infections [5]. This has lead to the recognition that the cleanliness of the clinical environment is more important than previously thought, and has renewed interest in the role that architects, engineers and facility managers might play in designing out infection.



1.  Health Protection Agency. Voluntary reporting of Staphylococcus aureus bacteraemia in England, Wales, and Northern Ireland January-December 2007. 2. Health Protection Agency. Voluntary surveillance of Clostridium difficile in England, Wales and Northern Ireland, 2007. 3. Health Protection Agency. Quarterly Epidemiological Commentary: Mandatory MRSA, MSSA and E. coli bacteraemia, and C. difficile infection data (up to October – December 2011). 4. Boyce JM, et al. Environmental contamination due to methicillin-resistant Staphylococcus aureus: possible infection control implications. Infect Control Hosp Epidemiol 1997; 18:622-7. 5. Houang ETS, et al. Epidemiology and infection control implications of Acinetobacter spp. in Hong Kong. J Clin Microbiol 2001;39:228–234.