ENVI RONMENTAL T RANSMI S S ION
Tackling environmental transmission of HCAIs
Surface transmission has been identified as an important route of pathogen spread, especially within the healthcare environment. Jade Pallett discusses viral and bacterial transmission and looks at the key issues and evidence.
Environmental transmission of pathogens has been a long-recognised mechanism for the spread of infectious diseases.1,2
While
this transmission can occur on any surface, the high traffic nature of healthcare facilities can increase risks of surface transmission.3 The healthcare environment is known to harbour a wide range of microorganisms, some of which are considered significant pathogens to humans.2
Generally,
microorganisms tend to prefer to grow and replicate in organic, moist environments. However, they can persist under dry conditions. Despite being able to culture and detect microorganisms on surfaces and in the air, assessing their contribution in causing infection/disease can be difficult. The potential for contaminated surfaces to contribute to the transmission of pathogens within the healthcare environment depends on a number of factors.4
These factors include the
ability for survival on a variety of dry surfaces, the frequency of surface contamination on areas commonly touched by patients and healthcare workers, and whether the resulting concentration of pathogens is sufficiently high to cause transmission to humans. Some pathogens, such as Clostridium
difficile, MRSA and VRE are able to remain viable on a range of surfaces for days or weeks, sometimes even months.5,6
Despite
multiple factors being required to create the conditions necessary in order for pathogens to be transmitted via environmental surfaces, environmental transmission is still a proven route of infection within the healthcare environment.
Similarly to bacterial pathogens, viral pathogens have been known to spread via surface transmission, although they tend not to be able to survive for such long periods of time. One study found SARS-CoV-2 to be able to spread readily around a patient’s room, with the virus spreading from the patient to 18 other surfaces in the same room within 10 hours.7
This highlights the importance
of environmental transmission and reiterates the need to tackle this form of spread, with focus on the healthcare environment. This additionally highlights a gap in the current infection control and prevention practices, as pathogens are being proven to spread and be harboured within the healthcare environment.
Healthcare institutions have reported outbreaks of both VRE and Pseudomonas aeruginosa linked to contaminated surfaces found within the environment and spread via healthcare workers’ hands.
DECEMBER 2021 Viral transmission
While viruses require a host cell to replicate, they are known to be able to survive on surfaces for extended periods of time.8,9
The
COVID-19 pandemic is still very much in the spotlight, with many worried about the winter months.10
SARS-CoV-2 to have the ability to survive on surfaces for up to 72 hours.11
One experiment has found This same
study found the virus to be highly stable at low temperatures. Published research discussing severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) (viruses closely related to that of the COVID-19 pandemic), has shown that both these viruses and influenza viruses can survive on surfaces for up to several months.13
One of the most commonly accepted routes of respiratory viral transmission is droplet transmission, where droplets containing viable viruses come into contact with a host’s eyes, nose or mouth and into the upper respiratory tract.14
Other modes of
transmission include contact transmission, either direct or indirect. Direct transmission
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