MERS joins the more-environmental-than-you-may-think club


I blogged about a review of the surprising ability of some respiratory viruses (especially SARS-CoV and Influenza virus) to survive on dry surfaces last year. In the review, I predicted that MERS-Cov would also share the same ability to survive on dry surfaces as SARS-CoV – so I was interested to see a recent article in CID demonstrating that MERS is indeed more environmental than you may think.

The team in South Korea investigated surface contamination with MERS-CoV identified by PCR and culture surrounding 4 patients with MERS-CoV infection in 2 hospitals. The study ended up being quite well ‘designed’ since none of the patients had any symptoms when sampling began, so serial clinical and environmental specimens were collected throughout the course of the disease.

Before we get to the results, I’d like to highlight a unique aspect of the methods. I’ve seen many reasons (excuses) as to why informed consent was waived – but I’ve never seen this one: ‘Informed consent was waived by the Review Board…to eliminate the possibility of spreading MERS-CoV via patient contact with the informed consent forms.’ Very topical given the subject of the study – although surely verbal consent would have been an alternative!

Viral RNA was detected all over the place (the authors describe this as “massive contamination” in the discussion). Overall, 30 (20%) of 148 environmental samples were contaminated with MERS-CoV RNA (see Figure below). The level of contamination with viable MERS-CoV was lower, with 6 (4%) of the 148 samples positive, in line with other similar studies. Concerningly, aside from a single radiography cassette that was sampled, the most heavily contaminated area was the anteroom tables, where you’d hope not to find any contamination at all! Here, 3/7 samples were positive for MERS-CoV RNA, and 1/7 grew viable MERS-CoV.Seo MERS env

Figure: Contamination on the environment with MERS-CoV, by sampling method and site.

Another alarming finding was that environmental contamination persisted for some time after symptoms had resolved / patients had moved out of the rooms. The duration of MERS-CoV RNA detection from environmental samples since the patient’s last positive PCR ranged from 2 to 5 days. It is not clear to me whether this is due to extended viral shedding once symptoms have resolved or extended survival of the virus on surfaces; I suspect it’s a combination of the two. It’s a shame that the article does not disclose the type of cleaning / disinfection that was performed during the study.

These findings confirm that an environmental reservoir needs to be taken seriously when dealing with MERS-CoV, and argues for bringing out the big guns when it comes to environmental disinfection (such as daily use of bleach and hydrogen peroxide vapour or possibly UV at the time of patient discharge).

Image: NIAID.

6 thoughts on “MERS joins the more-environmental-than-you-may-think club

  1. Jon,

    I agree that it is a shame that the cleaning protocols and chemicals used are not noted in the report.

    As I mentioned in my response to your initial posting on this matter the longer than expected survival rate of the virus on surfaces is highly likely to be due in large part to the presence of biofilm on those surfaces.

    Andrew also raised a good point as to the material of the surfaces that showed these unexpectedly long survival rates.

    The proposed use of the “big guns” (bleach, hydrogen peroxide vapour or UV) to address the environmental issues is a natural and common reaction. Such a response represents a set of products and protocols that appear to be increasingly less effective, and when such chemical solutions are used at the sort of concentrations often proposed in such circumstances, most are potentially harmful to the surfaces to which they are applied, dangerous to apply, and the anecdotal evidence suggests that they are becoming less effective.

    As for UV, I have doubts about the effectiveness for two reasons:

    (1) Is that I have seen research that UV (several spectrums were used) is not totally effective at addressing biofilm.

    (2) UV light rays don’t necessarily get to all the spots. I have seen this in HVAC applications and also in recent attempts to use UV devices to address hygiene issues on commercial aircraft.

    Now on a flat surface, with long exposure, UV may be effective.

    So my concern is that the use of stronger versions of what we have been using are struggling to keep up with the problems.

    Survival of viruses on surfaces in the absence of a host for longer than previously believed possible / likely, and the evidence of them being increasing resistance to conventional chemistry solutions suggests the need for alternatives.

    Addressing the formation of biofilm is I believe a key component.


  2. @ gmarsh01 Good point about biofilms. Jon, you blogged about biofilms on surfaces a few months back. Could you give us an update on research into biofilm formation on dry indoor surfaces, please?

    The only info have to hand about metallic copper surfaces and biofilms is: “…although biofilm formation has been reported for copper water pipes, this does not occur under dry surface conditions, and exposure to copper affects the ability to form biofilms.”

    Excerpt from:
    Warnes SL, Keevil CW. 2011. Mechanism of copper surface toxicity in Vancomycin-resistant enterococci following wet or dry surface contact. Applied and Environmental Microbiology, Sept. 2011. pp. 6049–6059.

    Welcome your thoughts on this, and any further research you can share.


  3. Following up on Andrew’s comment, our November paper in mBio ( ) showed the SARS/MERS-related pathogenic human coronavirus 229E remained infectious in a human lung cell culture model following at least 5 days of persistence on a range of common nonbiocidal surface materials, including polytetrafluoroethylene (Teflon; PTFE), polyvinyl chloride (PVC), ceramic tiles, glass, silicone rubber, and stainless steel. So presence of biofilm is not essential for coronavirus survival but as studies with poliovirus in water systems and elsewhere have shown, may exacerbate their survival.

    We have shown previously that noroviruses are destroyed on copper alloy surfaces. In this new study, human coronavirus 229E was rapidly inactivated on a range of copper alloys (within a few minutes for simulated fingertip contamination) and Cu/Zn brasses were very effective at lower copper concentration. Exposure to copper destroyed the viral genomes and irreversibly affected virus morphology, including disintegration of envelope and dispersal of surface spikes. Cu(I) and Cu(II) moieties were responsible for the inactivation, which was enhanced by reactive oxygen species generation on alloy surfaces, resulting in even faster inactivation than was seen with nonenveloped viruses on copper.

    Consequently, copper alloy surfaces could be employed in communal areas and at any mass gatherings to help reduce transmission of respiratory viruses from contaminated surfaces and protect the public health. So working 24/7 as an important adjunct to routine or emergency cleaning regimes.


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