ENVI RONMENTAL T RANSMI S S ION
does not involve contaminated surfaces, whereas indirect transmission refers to the role of contaminated surfaces within the spread of infection.15
It has been suggested
that indirect contact transmission is one of the predominant transmission routes for influenza, as well as some other respiratory viruses.16
There is also some evidence for the transmission of enteric non-enveloped viral transmission via surfaces, such as transmission of norovirus.18
There has previously been some scepticism surrounding the ability for enveloped viruses to survive for extended periods on surfaces.19 Despite this, several studies have been conducted that indicate respiratory viruses are able to remain on surfaces for a duration long enough to facilitate onward transmission.20,21 Respiratory viruses have also been found to readily survive in common environmental reservoirs such as sewage, foods or in water sources.22,23
It is noteworthy that severe acute
respiratory syndrome viruses, MERS and SARS-CoV-1, appear to have a higher rate of survival on surfaces than other human coronaviruses such as 229E or OC43.24,25 Therefore, there seems to be some variability in the ability to survive that is dependent upon the specific species of virus.
Of the numerous studies that have been conducted, there have been many different methodologies to assess the survivability of viruses on the surface. A range of different surfaces have also been tested, including those that are commonly used for PPE (personal protective equipment) such as gloves, gowns and respirators.26
some items of PPE were detected up to 24 hours after contamination.27
One common
denominator found across a multitude of studies was the effect of temperature and humidity on viral survivability to be consistent. Both coronaviruses and influenza viruses were found to have superior survival rates at lower temperatures and lower relative humidity.28
The need to consider the role of viral surface transmission is
often overlooked, more so than with other pathogens such as bacteria. However, as has been evidenced, indirect contact plays an important role in the spread of respiratory viruses and must be considered within infection prevention and control strategies.
Bacterial transmission Contaminated surfaces have been a long-identified route of transmission for bacterial pathogens of importance within the hospital setting such as methicillin resistant Staphylococcus aureus (MRSA), Clostridium difficile, Acinetobacter baumannii and vancomycin resistant Enterococci (VRE).17
The viability of both gram-negative and gram-positive organisms has been broadly described within available literature. Enterococci have been found to survive upon numerous fabrics found within the healthcare environment.29,30
In addition, certain fabric
upholstery materials have been found to have the ability to harbour VRE for at least one week after simulated contamination.31 Healthcare institutions have reported outbreaks of both VRE and Pseudomonas aeruginosa linked to contaminated surfaces found within the environment and spread via healthcare workers’ (HCWs) hands.32,33 Another study has demonstrated materials commonly found within the healthcare environment to have the ability to harbour multiple different species of pathogens, but found VRE, which is known to be environmentally hardy, to be especially prone to survival.34
Survival on
Acinetobacter spp. has also been proven to survive for extended periods of time within the healthcare environment. Hospital acquired infections (HAIs) caused by Acinetobacter spp. have previously been linked with contaminated surfaces and subsequent spread via healthcare workers hands to patients.36
Once established
within the environment, outbreak strains of Acinetobacter spp. can become endemic within certain work areas or institutions.
The mortality rate for patients infected with Acinetobacter spp. has been shown to range up to 50%.38
to control the environmental contamination of surfaces and fomites is of upmost importance in reducing nosocomial infection rates with the healthcare environments.
Importance of environmental transmission Surface transmission has been identified as an important route of pathogen spread, especially within the healthcare environment. Loftus et al, identify routes of transmission within the intraoperative environment for multidrug resistant (MDR) pathogens such as vancomycin resistant Enterococci.12 While it has been identified that a surface must demonstrate certain microbiological characteristics in order to play a role in transmission, it is also widely acknowledged that surface contamination does play an important role in the spread of infection. There is supporting evidence for a range of pathogens to have the ability to spread via non-direct contact. For example, there is significant increase in the odds of a patient acquiring MRSA when admitted into a room that has been previously inhabited with an MRSA-positive patient. Similar findings have been found in rooms of patients positive for VRE.35
There are numerous factors that influence the ability of pathogens to be able to spread within the healthcare environment, including surface topography of materials, the use of certain textile fibres, and choice of substrate for surfaces, walls and floors.31 Materials that are commonly found within the healthcare industry that have previously been found to have the ability to harbour bacterial pathogens include: countertops, bedrails, polyvinyl chloride, fabrics and healthcare equipment.34 Research has been carried out within an anaesthesia work area to study levels of contamination across several critical touchpoints during the practice of general anaesthesia. The mean level of
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Therefore, the ability to be able
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