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How Long Can COVID-19 Survive On Surfaces?

Uncategorized Apr 03, 2020

So the topic of today is going to be How Long Can COVID-19 Survive on Surfaces? And in order to get into this important topic, I need to discuss something called fomite transmission. But, before we begin I also want to clarify that the virus is called SARS-COV-2 and this causes a disease called COVID-19.  And in fact, I need to define what a fomite is because this is the whole crux of this issue about whether or not these inanimate surfaces are or aren't going to be contaminated, and what you do about them. And this leads into something called nosocomial infections, which are hospital acquired infections. And this issue of fomites, these are objects that can become contaminated with an infectious agent that can then be transferred to a new host. And that new host, we don't want it to be us, it can be another object. I'm going to be giving you some examples of real world objects that have been found to be contaminated with various different influenzas as well as various different SARS viruses leading into what we know about COVID-19, or this SARS new number two (SARS-CoV-2). In order to deal with this, I want to really go through the emerging literature.


And the first paper I want to look at which is talking about the persistence of this particular virus on inanimate surfaces came out on March the 4th, 2020 just a few weeks ago. Essentially this paper reviews three patients that had SARS-CoV-2 in Singapore and it tracked their history within the hospital between January 24th through February 4th. And what they discovered was that 26 sites were tested using a sterilized remoistened swab, very similar to the types of swabs that we use all the time for environmental monitoring after water damage for fecal coliforms and other types of a fungal microorganisms that might be present. And so they used these swabs to test common what are called high touch areas, but they also looked at floors as well. And the interesting thing here is that there were three types of patients, and we're going to get into the patients in a minute and where they were in the disease progression. Basically, these samples were collected over a five day window over a two week period, and this is due to the differences in the infections that these particular patients had.

So what they looked at is that there was twice daily cleaning of high touch areas using a common disinfectant. So what was very interesting is that they then cleaned the floor with a lower concentration of this particular disinfectant. And later in this live stream, I'm going to be going through what we know about which disinfectants should be used for disinfection of the indoor environment against influenza, and more importantly, against COVID-19, and which disinfectants probably aren't going to be suitable for that task. So stick around to the end of this live stream and we'll get to that a little bit later.

As well, what's very important about this first February or this March 4 paper, is that they mapped the cleaning regime to the patient infection stage. This is really important because this is the first paper which, as I said, focused on the infection in the environment. And what they found, again, we're talking about this sodium dichloroisocyanurate disinfect, which is a very common pool disinfectant actually and it's got a very high chlorine concentration and smells strongly of chlorine.

I'm going to be going through the first two patients and then we'll be getting to the third patient. We'll call them patient A and so patient A had their room sampled on day four and 10 and they were still symptomatic with the infection and the cleaning was performed or the testing with the swabs was performed after the cleaning. And the good news was that all samples were negative for COVID-19. Patient B was symptomatic on day eight and asymptomatic on day 11. Room samples were again taken after routine cleaning and again, good news, all samples were negative, but here we come to the real point and the crux of this particular publication.

Patient C had upper respiratory tract involvement with known pneumonia. They did have positive activity for COVID-19 in their stool samples, but they did not have diarrhea. And before cleaning of course the room tested positive in over 87% of the locations that were swabbed. And these areas did include an air fan. So this is a really important finding because it's concerning certainly within a hospital-type environment that if it was possible to swab an air extractor fan, it's possible that there could be transmission within the HVAC or air handling system within the built environment. So that's a really interesting finding in this paper. But they also discovered that 60% of the toilet sites, including the bowls, the sinks and the door handles tested positive. And so that means that there is a significant amount of transfer from the patient even in the absence of pneumonia into the greater room environment. And so we now move on to what we know and what emerged in another paper that came out on the 22nd of March and this particular paper was looking at the stability of COVID-19 in aerosols and on various different surfaces.

And in this publication, their conclusions were that COVID-19 can remain viable for up to three hours in the air and up to 72 hours on surfaces. So in the first publication they demonstrated conclusively that even with an asymptomatic patient you get transfer of COVID remaining viable on certain surfaces for some period of time and yet they can be successfully cleaned off. In this next paper at March 22 they're looking at how long this particular virus might survive both in the air space and then on surfaces. And their conclusion was that aerosol and fomite transmission of COVID-19 is plausible since the virus can remain infectious in the air for hours and for days on surfaces depending on the inoculum shed and the type of material that it lands on. So this is really, really quite interesting information. And in this particular publication, in a sense, they've done some really excellent work in this March 22 paper because they looked at the rate of survival or how long the virus remained viable or could be recovered from various different samples and they were looking particularly obviously in the air.

And this is a graph that I'm putting up. So anyone who's listening to this in podcast format, I'm going to track through what this particular slide shows. And so firstly, these scientists were looking at two different types of coronaviruses and the one that we're most interested in is the SARS COVID TWO. And so that is in the top most graph of this particular figure. And they were able to show that both coronavirus one and two survives happily in the air right up to three hours. Now what about when this particular virus may land on various different materials? Now the reason copper has been included is the copper is known to have a significant antifungal, antibacterial and now an antiviral property to it and it has to do with really the material properties of copper.

And I'm going to make that actually the focus of a livestream in its own right in a couple of weeks because this is definitely applicable to fungal decontamination as well. And so there is a good push towards switching over a lot of touch, high touch surfaces in buildings such as door handles and push plates in bathrooms and also entry doorways to copper because it does present with these significant antimicrobial properties. And so on copper, the viruses greatly reduce quite quickly and we can see on the graph that that is occurring in approximately 20 minutes.

Cardboard, you can see that the virus remains active for a longer period of time. You can see that there's a different decay curve in the percentage recovery and this would be one of the reasons why it is very likely that Amazon fulfillment is moving to increase the number of workers due to the probability that they need to reduce their handling times or introduce changes in their why they get stock out due to the fact that a virus can remain viable on cardboard. And so that is a significant risk. And similarly, stainless steel, the virus does remain for quite long periods of time on stainless steel, but the worst material is, in fact, plastic. So that is the key take home message from the March 22 paper.

We move into the published literature to March 23 and an excellent publication came out then focusing specifically on the surfaces that were able to be analyzed after the people came off the Diamond Princess. And so this was one of the first in a sense, Petri dishes that were, allowed scientists to have a very careful look at what was going on within the environment. And they discovered that this COVID-19 remained viable in cabin surfaces for up to 17 days after the cabins had been vacated but before disinfection had taken place. So really this is diverges from the paper that came out or was published the day before, which basically said that the virus only remains viable for 72 hours.

And again, we've got some earlier work that gives different numbers yet again. So of course that makes it very difficult in deciding how to deal with the built environment and the probability or not of whether or not there is persistent contamination of COVID-19 in there. Now, I now want to move into some other literature that is also looking at the persistence of viruses on materials and fomite transmission and I'm going to hope that this is going to complete the picture and, in fact, demonstrate that the March 23 paper with the data from the Diamond Princess suggesting that 17 days is the key metric is probably the one that we should be looking at as the upper limit for safety. And if we suggest that 72 hour surfaces remain safe, that may be putting a lot of people at risk. So I'm going to track you through why that is my conclusion by going into a new set of literatures that focus on influenza and viral and bacterial and fungal transmission on something commonplace, something that we touch all the time, and this is our currency or our bank notes and our coins.

And so a week or so ago I was actually interviewed on a current affair on this particular topic about fomite transmission on bank notes. And my conclusion, I'm going to put it up here was that we really don't know about COVID-19 yet, but certainly I would be saying a minimum of two weeks right up to potentially 17 days and I'm going to run you through why I reached that conclusion before.

In fact, before the 23rd of March paper came out because there was some pre-existing literature if anyone wants to follow up and see the show that was on about the rationale for why bank notes were, there was some resistance to some shopkeepers taking bank notes and coin currency and a move towards contactless payments. Mainly because of this risk of hand to mouth transfer or hand to face transfer after potentially coming in contact with contaminated currency. I'll leave that for you to do in your own right.

Now, the first publication that I want to look at came out in 2008 and 2008 research here. I've got the URL up here so you can retrieve the actual paper yourself. Many of these are free on PubMed or on the various different service and the aim of this 2008 paper was to assess the survival of influenza on bank notes and this is really a key paper that I would assume the authors of the paper that focused on the Diamond Princess infectivity have also reviewed as well and taken a consideration when evaluating the surface contamination. But getting back to the 2008 paper, they were looking at this issue of persistence of influenza. Now influenza, I must stress, is different to COVID-19. Influenza has a very different viral composition, different infection rates, but still it's been used as a surrogate to determine the infection of viruses or how common objects can transmit viruses.

Now what the scientists discovered in their conclusions or main findings were that recovery rate is dependent on the inoculum size and of course that makes sense because if you imagine infecting a group of bank notes for example, the heavier the sneeze or the more significant the cough or the greater the amount of particle deposition on it, it stands to reason that that is probably going to have some sort of concentration dependency in the ability of this to remain viable and then be transmitted to other people or objects. Furthermore, the respiratory secretions increase the duration of influenza infectiousness. That means, essentially, how much secretion was actually deposited along with just the aspiration of the droplets. And so that was found to be a significant variable as well and their results showed that influenza was able to infect cells for 12 days after these secretions were deposited on the bank notes.

And the key finding from this publication was when high concentrations of inoculate that is, a virus containing particulate matter, is mixed in with mucus and that then is deposited onto the bank notes for both influenza A and B as test surrogates. It is found that the persistence was up to 17 days, so this is another peer-reviewed paper which suggests that viruses can persist for long periods of time and the conclusions were that since hundreds of billions of dollars worth of bank notes are exchanged on a daily basis worldwide, the infection probability from hand contamination with viruses that are present on bank notes cannot be underestimated.

Now if we move on to another publication in this same arena about paper money and coins, this came out in 2014 and the aim of this research was to investigate whether or not paper money and coins could transmit nosocomial infections and I will say a little bit about the differences between paper versus polymer bank notes because polymer bank notes were essentially introduced probably as an alternative to the fact that paper based bank notes don't persist as long in real world use due to their composition and polymer bank notes last longer, but polymer bank notes also are less porous and therefore microbes that can potentially grow only on the surface rather than into the fibers of the bank notes.

But we will get to that as a discussion a little bit later as well. The aim of the 2014 research was to look at exactly what types of microorganisms could be recovered and they were looking at two types of environments here and they were looking at bank notes that were recovered from within the hospital and they found that there were high levels of microorganism or bacterium called staphylococcus aureus. Whereas bank notes taken from food handling premises were dominated by salmonella e coli, but again, staphylococcus aureus, and interestingly, when lab simulations were performed, they discovered that methicillin-resistant staphylococcus aureus was easily able to survive also on coins. Now this is really not a good result, but the conclusions which make this a very useful paper where that contaminated money and coins are a definite public health risk, especially when individuals simultaneously handle food. And the take home message is that bank notes and coins carry bacteria and fungi and act as reservoirs for antibiotic resistant bacteria like MRSA.

So, let's now have a look at some other research which came out, a paper in 2018 done on a currency in Pakistan. And what they were looking at was they wanted to assess again, whether or not there was contamination within the hospital environment, but also in adjoining markets and in other community sources. And this is an excellent piece of research because they typed out the different types of bacteria and ranked them in a rank order and they discovered that 97% of the notes were in fact contaminated and that the dominant microorganisms here again are a microorganisms well known to cause disease and they included Klebsiella, Staphylococcus, Pseudomonas, Citrobacter, Enterobacter, Streptococcus Shigella, Salmonella. Again, the paper goes into very good detail about all of the different microbial strains and where they were discovered. And the interesting thing here is that currency notes of lower denomination had much higher contamination levels.

And of course the reason for that is thought to be the much higher turnover of low denomination bank notes. As well, contamination levels depend on the age of the currency and of course the material used to make the currency. And this particular Pakistani paper was obviously pushing for the government to change over from paper to polymer. I haven't looked up whether that's occurred as yet, but their conclusions in their paper where that currency circulating in the hospital and the community were shown to be contaminated with highly pathogenic and some multidrug resistant bacteria and governments can help reduce the risk and spread of infectious disease by launching plastic polymer currency notes instead of paper. So I think that that is a fantastic piece of research and any microbiologists who want to look up the types of microorganisms, I encourage you to do so. But what about some of the later research?

Well, a new paper has also come out in 2020 and it was looking at whether or not personal unhygienic habits are to blame for the bank note contamination. And so that's a different take on the preceding publications that I've reviewed. And what they were looking at again was whether or not the contamination is caused by improper hand washing or going to the toilet. And those conclusions were validated by the results in their study. And again, the study can be found online at this particular URL, but they also found that people who count money by licking their fingers and then flicking through the bank notes, that also contributes microbes as well. And that's a new finding into the literature. And of course coughing and sneezing into hands and then touching bank notes and coin currency is another way that these objects, everyday objects can become contaminated. The conclusions in this 2020 paper were that money of course becomes contaminated with microorganisms from the human hand mouth or gastrointestinal track microbiota.

And this is further proof why bank notes are in fact dirty and should be treated with some care. And especially now with COVID-19 these objects in use every day can certainly act as a Petri dish in your pocket. We really don't want that, so be very mindful of this and move to contactless payment wherever possible. Now, obviously you're probably wondering, well what do we do about it? Well, certainly in the current affair show I discussed the fact that South Korea has used heating to deactivate virus on currency, paper currency, and also there is some potential for using UVGI, which stands for ultraviolet germicidal irradiation to contact disinfect and in fact sterilize if the time and duration and distance is correct, these bank notes. But what about other biocides because it's nice to focus on bank notes, but contamination with COVID-19 in the real world is going to be a far more significant threat to a lot more objects than just bank notes.

So we need to look at what's emerging in the literature about what biocides are appropriate. And an excellent publication has come out talking about this. And again, the URL is up here and it is talking about how we would go about deactivating COVID-19 with biocides. And this publication has reviewed 22 other papers and it covers coronaviruses like SARS, MERS, and the inactivation on common objects including metal, glass and plastic. And again, they're talking about the fact that those other viruses can persist on those objects for up to nine days. So you can see that there's a wide range of divergent opinion about the duration of infectivity that viruses can present with on common objects. In any case, ethanol used at between 62 and 71% has been shown to reduce coronavirus within one minute and bring the amount of inoculum down from two to four log10 so that is an appreciable reduction.

It's not a complete reduction, but it's pretty good. It's better than nothing. Sodium hypoclorite, the infamous bleach and the reason I say infamous bleach is anyone who is tuning into this who is attuned to the mould restoration and decontamination literature has probably heard the old furphy that bleach does not work. Well, that is completely false. Bleach is a very effective surface disinfectant and when sodium hypochlorite is used at the correct concentration for fungi, it's very effective. Similarly when used at even quite a low concentration at between 0.1 and 0.5% there, sorry, up at the upper range 0.5 you get a very effective decontamination of COVID-19 and again when glutaraldehyde-containing disinfectants are used at 2%, they're effective as well. I should stress that benzalkonium chloride containing disinfectants even at 0.04% have been shown to not be effective against COVID-19 and very low concentrations of sodium hypochlorite similarly are not effective.

Now, where can you get further information and credible information about what disinfectants to use in the liquid phase will be appropriate against COVID-19. In the coming weeks, I'm going to be talking about aerosol decontamination. I'm only talking about decontamination of surfaces in this particular livestream, but the US EPA have released a wonderful interactive website. And again, the URL is at the bottom of this slide and they talk about something called a list N and the list N essentially is a long list of disinfectants that are known to be effective and known to be what are called virucidal. And so we need to understand that disinfectants have different types of killing abilities and you have low grade disinfectants that are more appropriately called sanitizers. And then disinfectants have a greater ability to decontaminate, for example, bacteria, yeast and fungi and in some cases are antiviral. And this is the virucidal activity right through to sterilants, which essentially kill everything.

And for viruses we're really talking about denaturing because the virus isn't technically alive like a bacteria or a fungal or a yeast cell and this particular list N and allows you to key in the key ingredient in your disinfectant and actually see whether it's on the list. Now I've also put up the disclaimer that the EPA also put on list N, because not all of these disinfectants have been validated against COVID-19, but many of them have definitely been tested against other coronaviruses and the corollary on here is that even the EPA says that those disinfectants on list N should be applicable to surface disinfection of COVID-19, but again this is an emerging illness and pandemic and a lot more is going to come to the surface and be written about in the peer-reviewed and open source literature, unsure in the coming days and weeks. In any case, we are now moving up to what usually is my favorite section of these live streams, which is the news today and I do have two very interesting publications which have just come out and we will get to that now.

Okay. The first publication, we're changing tack a little bit here. I'm moving away from COVID-19, I want to get back to what I talk about week in week out, which is fungi, but on the way to talking about fungi, we all know that a lot of air composite timbers are easily affected by unwanted water damage leading to mould and bacterial contamination. Now that stands to reason. We've all seen warped composite particle board. We've all seen cheap timber backings on cheap furniture, bookcases for example, and we all know that plasterboard when it gets wet can warp and we understand that these are manufactured materials used extensively in the building industry.

This publication just came out on March 13, 2020, and it's talking about something called cellulose nano fibrils and something called green wood panels. And think about this green term as really, instead of using virgin woods and 100% wood to make panels, these plaster boards and composite timbers aim to use a lower concentration of virgin wood, which has long fibers and essentially, the trade off in using 100% virgin wood materials as against composite timbers is that you've got a difference in structural stability and in order to make them extremely strong, there has been a big push, certainly in the manufacturer and a requirement during manufacture, to introduce petroleum-based adhesives.

And also many of these also use phenol and urea formaldehyde, meaning that the furnitures or the composite timbers that go into new homes often contain levels of formaldehyde that are really unwanted and toxic in their own right. And so this publication came out and I've put the schematic up here. I'll let you drill through the schematic to see how you make a composite timber. But it's pretty basic. Essentially you put the wood fibers together, you heat them up and you compress them. You use two sheets of paper essentially to compress the material together and out comes a sheet of a composite material, be that plasterboard or be that wall timbers. So in a sense these scientists have been looking at using something called cellulose nanofibrils and a cellulose nanofibral really is, as it says, an interesting additive. And here we're looking at how the manufacturing process can be value-added by introducing a new material which could reduce the requirement of using these urea or phenol-containing adhesives.

But the thing is that you can't get rid of these phenol and urea-containing adhesives until you make sure that the end product is structurally strong and is fit for purpose. And so what these scientists have established is that when you introduce these nanofibrils or introduce other additives like starch, you are able to create a new wallboard which has a lot of the desired properties of increased tensile strength. And this is really a fascinating, fascinating paper and that's really all I wanted to say about that particular publication because it caught my eye when it came out in the last week and I thought it worthy to mention simply because there will be a requirement to improve on the existing products for a lot of reasons to reduce the concentration of formaldehyde that goes into the built environment, but not only that, we're going to need to validate a lot of these products to make sure that they don't, for example, end up warping more significantly than the existing products.

And that last paper showed that by adding boric acid along with the starch and these nanofibrils, boric acid is a well-known antifungal agent and I suspect that that publication will be used as the premise for a lot of claims to be made about the stability of these new generation materials to actually resist mould. And I think that these are very interesting initiatives and I urge anyone interested in the manufacturing of new building products to dig up this paper and read it themselves.

The last publication that also caught my eye, especially here in Australia, there's been some confusion about the stay at home rules concerning schools and school attendance and the impact that that would have on teacher exposure, but also exposure to other members of the family if children are asymptomatic and then are in the transmission phase of the virus to bring that home. And so this particular paper came out on the 16th of March and the aim here was to look at the virus survivability and whether or not this can cause indirect person to person transmission. And they were looking at this in high touch surfaces in seven kindergartens and several primary schools from 2017 to 18 during the winter influenza season in Hong Kong. So bear in mind that this is not COVID-19, this is influenza.

LiveStream Facebook Link:


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