Surface contamination and respiratory viruses with pandemic potential (SARS, MERS and influenza): an underestimated reservoir?

Droplet airborne direct and indirect contact figure_final

Most virologists would probably tell you that enveloped viruses are generally pretty fragile outside of their host and so wouldn’t survive for long on dry surfaces. They may well say “If you were talking about a non-enveloped virus (like norovirus) then, yes, it would probably survive on surfaces for quite a while. But enveloped viruses, no – you’d be lucky if it survived for more than a few hours.” But when I looked at the literature to investigate the potential for dry surface-mediated transmission of respiratory viruses with pandemic potential (SARS, MERS and influenza), the picture that emerged was quite different. These respiratory viruses can survive on dry surfaces for ages, and the contaminated environment may well be an underestimated reservoir for their transmission. This is summarised in a review published recently in the Journal of Hospital Infection.

Laboratory studies show that SARS-CoV, MERS-CoV and influenza virus can survive on surfaces for extended periods, sometimes up to months. Environmental sampling in field settings has identified contamination with SARS-CoV and influenza virus (no studies yet for MERS-CoV), but important to note that many of these studies used PCR to detect the virus, so there is often no way to tell whether the virus is alive or not. At the very least, detection of nucleic acid is a marker of shedding.

The figure above summarises the complex transmission routes of respiratory viruses. They are emitted as a ‘cloud’ containing a whole spectrum of particle sizes, from tiny droplet nuclei, which aerosolise, through to large, wet droplets. It is likely that both play a role in transmission. And they also come out of the other end (in faeces) is startlingly high numbers (e.g. 109 virus particles per gram of stool for SARS-CoV), raising the potential of faecal-oral transmission. Given the various potential routes of transmission, it is very difficult to disentangle which is most important. There is some compelling data from mathematical and animal models, and from intervention studies that contact transmission can be the most important route. But this is virus – and context – dependent. If you have 20 people in a lift, then the air is likely to be the most important vector. But if you have two people whose only epidemiological connection is shared contact with the lift call button, then surfaces are the only potential transmission vector.

Having now reviewed this extensive and wide-ranging and interesting literature, I have settled on the view that surface contamination is an important potential reservoir for transmission of these respiratory viruses, so should not be underestimated from an infection prevention and control viewpoint.

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5 thoughts on “Surface contamination and respiratory viruses with pandemic potential (SARS, MERS and influenza): an underestimated reservoir?

  1. Agree. An interesting study by Charles Gerba on spread of bacteriophage MS-2 as a surrogate for norovirus: how far, and how fast, did it spread from a contaminated set of door handles at the entry to a large office building?

    Gerba, C. et al. 2014. University of Arizona, Tucson, presented at ASM’s 54th ICAAC, (Sept 2014) Washington DC http://www.icaac.org/index.php/scientific-activities/asm-live-at-icaac/asm-live-archives/328-icaac-2014-how-quickly-viruses-cancontaminate-a-building

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  2. I believe, based upon considerable field experience and limited independent lab tests that it is the presence of pathogen biofilm on surfaces that establishes surfaces as an underestimated reservoir for viruses.

    The CDC and NIH have noted that viruses can exist in biofilms in the absence of a host.

    Biofilm is the much misunderstood and under appreciated factor in cleaning and public health and safety.

    Biofilm (again according to the CDC and NIH) can make pathogens between 500 Xs and 1,000 Xs more resistant to disinfectants by preventing these products penetrating the cell wall. Furthermore, virtually all cleaners and disinfectants fail to remove biofilm; they may damage it and or significantly impact it, but they don’t eliminate it. Given pathogen biofilms can replicate as rapidly as every 20 minutes, recolonization in such conditions is inevitable.

    As such the “housing” on surfaces that can “shelter” viruses remains in tact to varying degrees and as such is an underestimated reservoir for such viruses, and so a risk to public health.

    I believe that pathogen biofilm on surfaces represents Public Health Enemy #1.

    Addressing biofilm is essential. The rise in the number of Super Bugs, and their spread to public facilities other than hospitals, is in part representative of the increasing failure of heavy chemistry (bleaches, quats, oxidizers etc) to be able to address the issue.

    An alternative approach to addressing biofilm other than the conventional Chemistry and Physics protocols is increasingly necessary.

    Given that pathogen bacteria (including Super Bugs) and viruses are essentially a Biological problem then perhaps we need to consider a Biological solution.

    Introducing safe probiotic bacteria to the cleaning protocols provides a means of introducing a Biological solution to address this Biological problem.

    There is a good amount of history of the use of probiotic cleaners being demonstrated to be far more effective than conventional chemistry. They warrant serious consideration and further research.

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    • Andrew .. the majority of the data I have comes from a client of my consulting business who has been in the space for 7 yrs .. there is some data on their website: http://www.zbioscience.com .. In large scale poultry their probiotic cleaners have been the driver for farmer to go Antibiotic Free (ABF) whilst also cutting the mortality rates of flocks (broilers and turkeys) by more than 50% and helping reduce the time to achieve harvestable weight by 10%. Farmers have indicated that they save / make 5 Xs what they spend on the probiotic cleaners (there is a testimonial from one on the website – Diestel Turkey which is the primary supplier of Organic and Natural Turkey deli meats to Whole Foods, so a sizable and reputable end user. The data on the pig farm with PEDv was shared by the farmer to one of my client’s distributors; I will see what written data has been produced – farmers are notoriously reluctant to share in what is a highly competitive sector. They aren’t like the folks in the healthcare sector. Graeme

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  3. Completely agree on the seriousness of surfaces when considering halting transmission. Not thought through enough and probably a major contributor to recent MERS healthcare outbreaks, but also the hundreds of other propelled human respiratory viruses needlessly spread in these settings.

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