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Surface Testing for COVID Can Reveal Pre-Symptomatic and Asymptomatic Hotspots

Uncategorized Jul 06, 2020

Hello, my name is Dr. Cameron Jones, and I'm an Environmental Microbiologist, and today, I've got a very important show on. The reason for this is because obviously, all of us are being affected by the coronavirus, and our laboratory is certainly undertaking whatever we can do to help with coronavirus identification, especially of sites that may harbor COVID-19 cases. How are we doing that? Well, I'm going to explain to you. Over the last couple of weeks, I've been talking a lot about surface contamination.

Obviously, all of you would be familiar with the concept of clinical testing, that is the nose or throat swab collection, to determine whether or not you are presymptomatic, asymptomatic, or actually have symptoms of COVID-19, but what about the level of environmental contamination? That's what we're going to be focusing on today.

I'm going to be reviewing what certainly I and my lab has learnt about this over the last couple of weeks and months, and I'm going to be reviewing two publications that have come out very recently. One, most recently, 24 hours ago on the 3rd of July in the United States, and then one from a couple of days ago on the 29th of June. Each of these papers is focusing on environmental contamination, because this is the other important thing that we need to be taking into consideration, so I'm going to get into the topic of today's talk, and that is something called Sentinel Environmental Screening for the Coronavirus.

Now, what do I actually mean by Sentinel testing? Well, we're going to get into that, but before I do that, I want to review this fantastic paper that came out, as I said on July 3rd. This is by the United States Army Medical Research group, and what this publication is stating, and I've said it before as well, that environmental surfaces can remain contaminated with the coronavirus for long periods of time, and in fact, I'd urge you to go to medRxiv and download this paper yourself and read it, but I'm just going to summarize some of the key points from their paper, just to emphasize exactly what we're talking about today. These researchers were interested in the persistence of the coronavirus, and they looked at this on various types of currency, the $1 and $20 banknote, but I'm much more interested in the top line of this table, which shows you the positive samples, that is swab samples that have been collected from skin. You can see, in reading from zero hours right across to 72 hours, which is three days right up to 336 or 14 days, and this is actually showing you that the virus remains on these surfaces for up to 14 days.

Really, this is a very incredible result, but it's very sobering as well to think about the implications of this. Not only that, then you can see that the virus is remaining replication competent even on clothing right up to four days, and the paper, if you drill into the results, you can find out that there is a very strong connection (or correlation) with temperature. Again, we've talked about the contribution of temperature and relative humidity before, but the take-home message that I want to start as my premise to this presentation is the very fact that the coronavirus remains replication competent on surfaces for long periods of time. Now, you might be thinking to yourself, "Well, he's just paranoid," but I'm not, and the literature supports my premise, but the question is how risky is environmental contamination? Well, the whole aim is to use these sorts of surrogate indicators, swabbing the environment, to detect those individuals in the community that may be virus spreaders or even super spreaders. How do we actually go about doing this?

Well, all of you would be familiar by now about the importance of face masks. Really, that is because of the airborne coronavirus shedding, which occurs naturally into the environment when people cough, sneeze, even sing, and when they're talking to one another. Depending on the amount of mucus and other material that may be shed during that aerosolization event, this can become airborne, as well as settle out onto surfaces, especially in confined spaces. Now, once this occurs, these virus particles are deposited onto surfaces, and they can persist for hours to days, as we saw with the latest U.S. military research. Now, the practical implications of this are that it is not practical to test every person every day in the workplace using clinical testing, e.g. nose or throat swab tests.

What are we going to do then, and who are we going to focus on, and what are we going to focus on?

Well, I want to review the various different types of how we can actually catch COVID-19. In a sense, we can all come into contact with other individuals, and the literature research shows that

  • 46% of the contraction of coronavirus occurs from presymptomatic individuals, that those are those individuals that don't show symptoms.
  • Now, 10% of the virus transmission between people is from asymptomatic individuals. That's people who never show symptoms.
  • Now, 6% of transmission occurs via this surface to mouth or fomite transmission, or between people. Again, we're focusing on that today, but this is linked, this fomite transmission, to the concentration of potentially presymptomatic people present in the workplace, who can potentially infect others, and this is where the increasingly important role of the environment comes into play.
  • 38% of exposure also occurs with obviously symptomatic individuals, and we can all visualize that if one member of your family has the coronavirus. It is potentially plausible and probable that you could become ill yourself if you have been in close proximity with them. The issue is that exposure with presymptomatic people can occur five days before symptoms, and this phenomena is thought to be the leading cause of infection.

What are some of the options to control the spread of coronavirus? Well, obviously, frequent environmental disinfection. There are, of course workplace procedures, policies and procedures that can be developed, including fitness for duty screens. They may include temperature checks. Any of you who've been watching the technology media would be familiar with the application of infrared thermal imaging and laser-based temperature pointers, all of these are technology-assisted methods to screen large numbers of people quickly, and the aim here is to pick up early, individuals who may be carriers of the virus.

Furthermore, social distancing…all of us are undergoing and complying to a greater or lesser extent with social distancing expectations, often suggested or mandated by government. Certainly, here in Melbourne, in the last 24 hours, there's a new lockdown in some social housing estates due to the fact that a cluster of unwell individuals has been detected there. Now, there are various work-at-home policies that can be implemented, as well staggered shifts in the workplace, as well as small team segregation. This is an overview of the options to control the spread, but really, the primary reason for workplace control failure is essentially the inability to detect pre and asymptomatic carriers, and today's livestream is going to focus on the role of environmental surveillance in order to detect these pre and asymptomatic carriers.

Now, unfortunately, unless control measures like temperature checks, and working from home, and social distancing are uniformly applied to everyone, it's just not going to work, so virus carriers are going to continue to shed the virus into the environment, the work environment, which will then lead to further unknowing exposure to other persons to a steady stream of virus laden air, as well as surface contamination. Now, new research shows a very significant and plausible and practical solution, which can be applied. Now, I want to refer you to this excellent paper, which came out on June 29th, again in the preprint server medRxiv. This is talking on Sentinel Coronavirus Environmental Monitoring.

The aim here is to use environmental swabbing to identify those locations that are probably hiding individuals who are carriers of the coronavirus, but they might not have been tested yet, and so what did this research show?

Well, I'm going to summarize it for you now, and I'm going to give you some practical tips that you can use to identify these high-touch surfaces that you and your cleaners should probably pay particular attention to. The research reviewed nine workplaces in the United States and in Europe, and what they did is that each of these workplaces already had developed and implemented COVID-19 control plans. In a sense, think of this as like the Australian COVID safe workplace suggestions and recommendations. These businesses that were reviewed in the literature and that were the part of the experiment, they were small to mid-sized urban and suburban class A or B offices, as well as mixed-use industrial buildings. As well, the researchers looked at a not-for-profit, a faith-based organization with 600 staff and 3,000 residents.

The research showed that what they did actually is that swabs were taken of the environmental services, as well as clinical swab testing of the people. What they did is that they daily-tested at least 15 locations per site, and they referred these as Sentinel surfaces, and these were those surfaces that are most likely at risk for other people to come into contact with. Over a two-week period, over 841 clinical tests were done. Those are the nose or throat swabs, but over 5,500 surface swabs were taken, so this is a massive experiment, which is being reported on, and the ... I'm going to jump to the results shortly, but I bet you're all wondering, "What are these surfaces, which could potentially be harbouring the coronavirus?" Even if you don't go to the trouble to download and read this paper, I've made a short summary of all of those surfaces and high-touch points, which were tested as part of this experiment.

These are the areas that you or your cleaners must focus attention on, so we'll play that now.

  • Floors
  • Door handles,
  • Knobs, & push plates
  • Walkway, stairway hand rails
  • Copy machine touch pad and cover
  • Shared keyboards, mouse, ipads, phones,
  • Headsets, PDAs & remote controllers
  • Time clocks
  • Door/gate/elevator keypads & buttons
  • Light switches
  • Table/bench/desk tops near seating area
  • Drawer/cabinet knobs
  • Chair back tops, armrests & seat sides
  • Sink faucet handles/knobs
  • Cleaning supplies – broom/mop handles, spray bottles,
  • Soap/sanitizer dispensers if not automatic, & towel dispensers if not automatic
  • Forced air hand dryers
  • Trash bin rims & lids
  • Appliance/equipment control panels,
  • Touch pads, control knobs & handles
  • Coffee dispensers
  • Utensils & tools
  • Vending machine touch pad & product dispenser chute
  • Toilet flush handles, knobs & seats
  • Toilet room stalls doors & latches
  • Feminine napkin dispensers
  • PPE storage bins
  • Employee lockers
  • Log books
  • Air handling unit vents & filters

Well, it's a pretty obvious list of surfaces, isn't it, and it makes a lot of common sense, doesn't it, that these are going to be high-touch surfaces that we come into contact with all the time, and that really, million-dollar question is, "How carefully is the cleaning being applied to those surfaces to make sure that residue of the coronavirus is not present, so the next person that comes into contact with these surfaces doesn't unknowingly become infected?" Let's have a look at what the results were. Well, the rate of coronavirus detection was 13% on these surfaces. This is very similar to earlier research out of Brazil, that suggested that 16% of surfaces would be contaminated with the virus, and if any of you watch my live streams, we went out to a suburban shopping center the week before last, and our hit rate for surfaces that were contaminated was 20%.

The greatest rate of surface detections corresponded with the detection of clinically positive employees. What does that mean? Well, it means that if you find it in the environment on surfaces, you got a high chance of finding someone in that immediate area who is a carrier of the coronavirus. Several days after clinical testing, lots of the immediate environment was actually contaminated. That means when there is clinical testing in suburban shopping centers and those sorts of environments, there is likely to be shedding of the virus into the environment, meaning that it is possible that someone could pick up the virus unknowingly, even though testing might not be going on there any longer. It should be remembered that in at least this research paper, looking at these over 800 some persons who were tested, remember 5,500 surfaces, none of the people who tested positive for COVID-19 were displaying any symptoms, and that is the frightening fact.

Another very concerning problem, highlighted by this research was that success of testing on different days of the same and similar high-touch objects returned a failed result, meaning that even though the cleaners were diligently applying their normal day-to-day work practices, they were not successfully removing the virus, and so the next question you might be asking yourself is, "Does this mean that cleaning isn't effective?" Well, a little bit of yes, a little bit of no. It does mean that cleaning service practices or the methods and chemicals used need to be applied properly, and the way in which this occurs is fundamentally important and impacts on this success outcome of the cleaning, or the post-cleaning validation, which is essentially what surface environmental screening or Sentinel testing in the environment is all about. Let's get back to some of the take-home messages about what this research showed. Well, at those locations where SARS-COVID-2 positive employees were identified, there was a very strong connection with finding at least one or more highly contaminated high-frequency touch points.

Because every single employee did pass a fit for duty test, it would mean that the only way to uncover or detect these individuals would be to test them daily, and that is just not practical and is highly invasive. It is much easier to test the surfaces. Now, every time they detected a positive surface, that is a surface failed, it revealed the presence of the SARS-CoV-2 virus, it meant that there was a connection with at least one clinically positive employee. The take-home message was that environmental testing is a very useful tool to inform clinical testing in order to detect the asymptomatic and presymptomatic spreaders, and the key conclusion, which is right in the final paragraph of the abstract, workplaces with surfaces that showed the coronavirus were 10 times more likely to have clinically positive employees working in the immediate area. That means that environmental monitoring can be used to validate intervention strategies and be used to verify the effectiveness of such strategies on a regular basis.

Now, that's all I wanted to say this week because I think these two publications have done a fantastic job of positioning the often overlooked role of environmental monitoring. This recent paper calls it Sentinel monitoring, and really, that is taking a whole range of surface samples from workplaces in order to determine, not just if the workplace is clean, but whether or not those employees that are working and operating in that workplace are potentially presymptomatic or asymptomatic, because we just don't know what the outcome of the illness is going to be in different people. For some people, it's fatal, for others, they don't even show any symptoms of illness. Therefore, without screening the entire global population day in, day out, we need to move towards surface testing of the environment in order to identify hidden clusters of infection. In any case, stay well, wear masks, use hand sanitizer, and I'll see you next week. Bye for now.

YouTube Link


Sentinel Coronavirus Environmental Monitoring Can Contribute to Detecting Asymptomatic SARS-CoV-2 Virus Spreaders and Can Verify Effectiveness of Workplace COVID-19 Controls
Douglas Marshall, Frederic Bois, Soren K.S. Jensen, Svend A. Linde, Richard Higby, Yvoine Remy-McCort, Sean Murray, Bryan Dieckelman, Fitri Sudradjat
medRxiv 2020.06.24.20131185; doi:


Modeling the Stability of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) on Skin, Currency, and Clothing
David Harbourt, Andrew Haddow, Ashley Piper, Holly Bloomfield, Brian Kearney, Kathleen Gibson, Tim Minogue
medRxiv 2020.07.01.20144253; doi:



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