Hi… I’m Wendy Zukerman you’re listening to Science Vs from Gimlet. Today on the show: is this coronavirus airborne? This is on everyone’s mind right now - as we’re wondering - could we get infected from the air - like when we go outside and no one is around? Is it safe to go for a walk?
Our producer Rose Rimler tried to figure this out. And her research took her down a really surprising path - back in time.. And all the way up today. Rose takes it from here.
RR: Back when we were first learning about this coronavirus one of the things that I found the most reassuring was what we were being told about how it spreads. Experts were saying that it passes through droplets- the stuff that sprays out of our nose and mouth when we cough or sneeze[1]. And I was like, great. That’s fairly easy to avoid right? I mean when is the last time someone actually coughed in your face?
But then I read these papers coming out showing that something else is going on too - this coronavirus is trickier than we first thought.
<<music post>>
And the idea that this coronavirus could be airborne really freaked me out. Because when a virus is airborne… something about that just feels scary. I mean, the first thing that comes to my mind when I think of airborne diseases...is actually an episode of the Simpsons...an old Halloween episode. Where there is this scene about a fog that turns people inside out sneaks in through the Simpsons’ window. It looks like a green cloud...making an evil hissing sort of noise. Then the whole family screams and turns inside out[2]! So that’s what I think of when I think of airborne diseases...a toxic cloud traveling from house to house...and there’s no escape.
RJ when you say something might be airborne or inhaled that raises the specter of vicious microorganisms traveling through the air round the globe office to office building-01
it's a very threatening feeling-01
This is Rachael Jones, associate professor at the University of Utah, she told me this question about whether this virus - or any virus - is “airborne” is actually controversial...which surprised me. To understand why it’s controversial...you have to understand the history. We have to go back about a hundred years ago.
RJ people were starting to have real problems in military hospitals with infections that were occurring and people were trying to figure out how these diseases transmitted[3]
Back then - scientists didn’t know how viruses and bacteria spread from person to person, although they had some hunches. When sick people cough and sneeze...they thought mayyyybe - there’s something in the stuff that comes out of their noses and mouths. But how could they prove it? One way was to put petri dishes in a room with people coughing and sneezing….[4][5][6]…
RJ it's basically you're putting out a little bowl and you're going to see what lands in it
RR that's not a terrible idea really
RJ no it’s absolutely not a terrible idea!
And what they thought might happen -- did! -- bacteria started to grow on the dishes. So they knew -- their hunch was right. Germs could come out… travel through the air … and then land on the counter or the petri dish or the floor ... They started calling the big gunk that came out of people’s mouths when they cough or sneeze --droplets[7]..
RJ and this is the origination of the idea of droplet transmission[8]-01
RJ these large droplets that they can see those particles visibly when somebody is coughing and that you can actually feel land on your face[9]-01
RR gross
Voila. Getting sick from droplets was officially discovered.. But, scientists realized this couldn’t be the only way sicknesses were spreading. They knew some diseases were really sneaky. Because sometimes people were getting sick when they were nowhere near an infected person … take smallpox, for example[10].
RJ classic case where smallpox was transmitted through a building to another floor out and a patient became infected third floor having never contacted the person on first floor[11]-01
Something else was obviously going on here. But what? Enter a Harvard professor named Wiliam Firth Wells[12]... He was a veteran of WW1[13]... had a mustache... puffed constantly on a pipe...[14] William wanted to prove that disease were traveling through the air -- so he designed a fluffier kind of experiment.[15]
He and his team moved a colony of guinea pigs into the tuberculosis ward of a hospital in Baltimore[16]. The patients didn’t get to play with the guinea pigs… the guinea pigs were put away from the patients - in the air ducts. - so the guinea pigs couldn’t get coughed on … but they were breathing the same air as the TB patients.[17] William maintained this colony-- actually, his female assistant maintained the colony[18]-- for years. Over that time, a hundred guinea pigs got infected with TB from the patients in the hospital[19] ….and eventually so did the female assistant.[20]. Anyway...
RJ that gives rise to the concept of airborne transmission[21] [22]
The thinking goes like this: for airborne diseases, you are breathing out teeny bits of liquid that have viruses or bacteria in them ... this stuff can survive in the air after you breathe it out, even after the liquid evaporates... and these dried up germs might get carried far away[23][24][25]. Yknow - compared to those droplets that are heavier so they fall to the ground faster.
And so, for a long time that how we thought about these diseases: airborne OR droplet[26] Two separate things. On team airborne TB, and Measles. On the team droplet there’s the flu and whooping cough.
RJ Correct, yeah
But now … things are changing. We’re finding out these categories are a lot muddier than we thought[27]. And it’s not because people like William Wells were dummies … It’s because we have way better technology[28] [29]. We don’t have to rely on petri dishes or sick guinea pigs anymore. Now, we have the tools to actually pull stuff out of the air - particles that are called aerosols.
RJ now that we have more sophisticated aerosol techniques we can measure particles that are very very small and particles that are large-01
Now we see that for some diseases that we thought were “droplet” diseases … you can find little particles hanging out in the air too. Take the flu. Researchers have had people with the flu talk into a cone … and then they collect the air that comes out of their mouths. In that air - their breaths - they found little bits of flu virus.[30]. Other studies have found that these viruses can actually move across a room[31][32] and potentially infect someone[33] [34]. So much for the flu being a droplet disease!
What this means is that for at least some diseases … you can get sick via droplets … OR from the air.
RJ we now have data, to demonstrate that droplet and airborne can actually occur simultaneously when a person is standing close to the sick person who's releasing virus into the air-01
RR and then science wise it's 2020 ...
RR we're kind of hung up on this, it's droplet not airborne it's airborne and not droplet, what does the science today tell us about that distinction?
RJ i think the science tells us today that that distinction is not particularly helpful
So basically, there isn’t an obvious line that separates airborne and droplet. But some viruses seem to do better in the air than others. Like smallpox and measles.[35] [36] So what does this mean for this coronavirus?
RR We, we told our audience, well, this is primarily spread by droplets which was a little bit of a reassuring message. So did we get it wrong?
RJ well i think. hmm. pause. i think it's incomplete laugh
WZ: The complete story, coming up after the break …
BREAK
Welcome back. We’ve just found out that - despite the Simpsons and Hollywood blockbusters screeching.. IT’S GONE AIRBORNE… the distinction between a virus that is “airborne” and one that isn’t - is muddier than it might seem. And, there are diseases… that we don't normally think of as airborne... which can actually travel a little in the air.[37][38][39][40] So what does all this mean for the coronavirus now?
To find out we called up Zhi Ning from the Hong Kong University of Science and Technology[41]
ZN Hi Wendy!
WZ Hello!!
Over a month ago as this virus was taking hold in Wuhan[42]… Dr Ning was watching … and wondering ...
ZN We had a big question in our mind, is how this virus can transmit in the air, how far they can spread, and how much harm they can cause to the human being … we want to know more.
So he got in touch with some colleagues in Wuhan - and they decided to start testing the air in a bunch of places around the city.[43] And to sample the air … they don’t just wave a glass jar around and quickly screw the lid on … they use a machine that’s a bit like a fancy vacuum cleaner…
In a way we have this active pump… we can suck the air through a filter
That filter is specifically designed so that it catches genetic pieces of viruses… and then back at the lab - they’ll see if they nabbed this coronavirus. Now, Dr. Ning's test can only measure the genetic material of the virus - using this method we can't actually be sure that any of the virus he might find would still be "alive" [44] [45] but based on other similar tests done by different scientists - we think that at least some of them would be[46]. So, knowing all that, one of the first places they looked - were spots where there was bound to be a lot of virus. Hospitals- where patient after patient with coronavirus had come through [47]…
ZN You could imagine how dangerous these places could be
The researchers put on big quarantine suits… and tested all around the hospital… even going into the health workers changing rooms
Went into the room and hold the samples in the air
So what did they find? Well when they looked at the hospital air …in some rooms where there coronvirus patients they couldn’t detect any viral bits.[48]
but in a few hot spots locations we did see some of the viruses.
One of those hot spots was perhaps not where you might expect. It was the bathroom-- you see, the had hospital makeshift toilets.
Yes indeed, indeed, the toilet is very simple mobile toilet without ventilation
And it turned out the air had a bunch of viral particles in it… Dr Ning couldn’t help but wonder.
But where do this virus come from?
He figures there are two main explanations. The first … is the obvious one: The breath of patients. As they pooed and weed they also might have breathed out viral particles into the air - and since the toilet was poorly ventilated, the particles just hung around there. But there’s a second explanation too - one that’s a little more intimate. Because some studies have found that virus bits can be found in feces[49][50][51][52][53].
And this feces may find it’s way in use of toilet time, and it probably can re-aerosolised into the air[54]
WZ: Oh so when people flush the toilet it goes hoo! Possibly puts viral particles in the air
Yes indeed because the flushing of the toilet, or even general the movement of the water, that can stir the water, the liquid and aerosolise the liquid droplets[55]
WZ So close the lid is one of the messages of your study?
Indeed indeed let’s do that
And viral particles weren’t just found in the air of the dunny. Another hot spot that showed up in the hospital was the room where healthcare workers took off their protective gear. And the air in that room was pretty contaminated, which was particularly interesting to Dr Ning, because the thing was all these hospital workers had all been tested and didn’t have coronavirus[56].... And they were the only people that went into that room. No patients.
The patients cannot get in the public cannot get in.
This suggests the viral particles might have got into the air like this. As the workers came into contact with patients, they also came into contact with the virus… from the patients coughing or sneezing or breathing or what have you … The virus landed on the hospital workers’ gear ... and when the workers took it off - the viral bits flung into the air.
So the movement of your arms once you take off apparel, they can find a way to become airborne
And it can stick around in the air. In a separate study scientists who spritzed this coronavirus into the air in A lab, found that some of it was still there, 3 hours later[57].
So that's the hospitals. What about other places - places we all go to? Well… Dr Ning's team also sampled the air at a supermarket… around a University and a residential building. And they didn’t find coronavirus in the air[58]
But it wasn't all good news. Dr Ning did find something concerning: Viral bits hanging out inside a department store entrance - where he reckons dozens of people were walking in and out.
Often times there are patients who don’t know they got infected, and when this is the case, when they walk around, and they talk you potentially can infect other people, but they don’t know, that’s a very dangerous side of this coronavirus
Of course our next question is: if I was walking through that department store entrance at that time... would I have gotten sick?
Z I think there is a there's a few steps -in the middle- to jump to that conclusion.
You see once the virus gets into the air it has a few more hurdles to clear before it infects me.
First I’d have to breathe it in… because we think this virus has to get into my body to gain a foothold[59][60][61][62][63]. So if I walk through a cloud of coronavirus and the virus lands on my shirt or my skin… I’d probably be ok… But say it does get into my mouth…
Next hurdle? I have to breathe in enough viral bits to make me sick[64][65] …we don’t know the cut off for this virus.[66] How many viral particles would make me sick… it is possible that maybe I wouldn’t have breathed in enough.
Ok so what are we to make of Dr Ning's study? Well yes this virus can be found in the air. But it's not everywhere - and other research is finding this too…like a few small studies[67][68][69] looking at rooms where coronavirus patients are being isolated -well they only detected virus in some of the rooms they tested. And the uncontaminated rooms tended to be well ventilated.[70] So it's looking like we have to be particularly careful in poorly ventilated places, and places that have been visited by lots of people. Oh, and close the lid of the toilet.
But there's still so much we don't know here. And we did find one study that threw a wrench in the works. It got a handful of patients to breathe and talk near an air sampler - only 4 inches away - they couldn’t pick up any virus from them.[71]
Do your findings give us reason to panic?
We don't have to panic saying we can not even breathe air anymore. I say we should be more cautious… because we know … that's the word… more cautious, cautious, cautious
Even with everything we're learning about this virus in the air ... scientists still think a lot of the time it is spread by those classic old droplets[72]...sneezing, coughing, that kind of thing or - a way we haven't talked about yet - through touching something that's been contaminated... ... and that part raises a ton of questions for people... about how they can protect themselves. Like what are you supposed to do about your packages? Your groceries? Your Bed? Your kitchen counter? Your dog? We're hearing this virus could be everywhere... like evil glitter… so is that true... and how cautious do you really have to be? That’s coming up next MONDAY....
But before we say toorah, let’s change gears. Time for a bit of NCVC - non coronavirus content…
<<JINGLE>>
I want to tell you about dolphins. Yeah. Researchers have found very recently that male bottle-nosed dolphins near Western Australia sing together - boy band style - when they’re trying to pick up a female.[73] Scientists already knew these guys sync up their body movements to attract a mate.[74] [75] [76] But now, they’ve caught groups of dolphins singing together, too... These animals are N’Sync!... at 600 beats a minute[77]! The researchers sent us the dolphin sounds they recorded.[78] Here’s one dolphin singing alone:
ONE DOLPHIN NOISE
And here are the dolphins singing together…
MULTI DOLPHIN NOISE
Hear it? And. Unlike boy bands, these dolphins - sometimes they stay together for decades.[79]
That’s Science Vs.
CITATIONS
CREDITS
This episode was produced by Rose Rimler, Wendy Zukerman, Michelle Dang, Meryl Horn, Sinduja Srinivasan, Laura Morris, and Meg Driscoll. We’re edited by Blythe Terrell and Caitlin Kenney. Fact checking by Michelle Harris. Mix and sound design by Peter Leonard. Music written by Peter Leonard, Emma Munger, and Bobby Lord. A big thanks to all the researchers that we got in touch with for this episode, including Prof. Natasha Crowcroft, Prof. Linsey Marr, Dr. Stephanie King, and Noah Miller. And special thanks to the Zukerman family and Joseph Lavelle Wilson.
I’m WZ, fact you next time.
[1] Our first coronavirus episode: search for “droplet”
[3] Infectious Disease late 19th century, early 20th:
https://www.sciencedirect.com/science/article/abs/pii/S002571251636518X?via%3Dihub WWI
https://www.ncbi.nlm.nih.gov/books/NBK218224/ See 19th Century - Sanitary Problem
[4] See Koch, Cornet, Flugge, Buchner, Emmerich Flugge and Hippke: asked patients from sanatoria and hospitals to cough for 1 h daily over at least 3 days; 70/158 (38%) sanatorium patients and 36/72 (50%) hospitalised patients now coughed bacilli-containing droplets.
[5]In 1897 Flugge (36) called attention to the possibility of microorganism being carried in droplets and bubbles. Flugge (36) and his associates, with bacillus prodigious in their mouths, speak loudly, sneezed and coughed in a room where agar plates had been exposed. They thus proved that by such acts droplets or minute particles of mucus are ejected from the respiratory tract into the air.
[6] is generally involved the instillation of a harmless indicator organism, such as Chrornobacterium prodigiosum, into the mouth, catching the expelled droplets on culture plates, counting the numbers of colonies after incubation and assuming that the number obtained bore close relationship to the number of droplets expelled. By this method Flugge, and more particularly his pupils and successors, Lastschenko (1899), Doust & Lyon (1918) and Winslow & Robinson (1910), ascertained that very few if any droplets are produced during quiet breathing but that they are expelled during activities such as talking, coughing, blowing and sneezing. Flugge (1897) showed that droplets from the nose and mouth contained bacteria, but did not travel more than 2 m.
[7] Droplets are too large to be airborne for long periods of time, and quickly settle out of air….
Airborne transmission refers to situations where droplet nuclei (residue from evaporated droplets) or dust particles containing microorganisms can remain suspended in air for long periods of time. These organisms must be capable of surviving for long periods of time outside the body and must be resistant to drying. Airborne transmission allows organisms to enter the upper and lower respiratory tracts. Fortunately, only a limited number of diseases are capable of airborne transmission.
[8] Early aerobiologists were not able to measure small particles near an infectious person and thus assumed such particles existed only far from the source. They concluded that organisms capable of aerosol transmission (termed "airborne") can only do so at around 3 feet or more from the source. Because they thought that only larger particles would be present near the source, they believed people would be exposed only via large "droplets" on their face, eyes, or nose.
[9] Droplet transmission occurs via large droplets that are generated by a close expiratory event (coughing, sneezing): they deposit immediately onto a susceptible's mucous membranes.
[10] Rarely, smallpox has spread through the air in enclosed settings, such as a building (airborne route).
[11] An Airborne Outbreak of Smallpox in a German Hospital and its Significance with Respect to Other Recent Outbreaks in Europe* See figure 2
[12] I was studying sanitary engineering at Harvard but had run out of money. ….I was awarded the fellowship with Professor Wells as my tutor. The financial aid was welcome but I had no idea for a project and had not met Professor Wells. Wells taught in both the School of Public Health and the Engineering College and his office in Pierce Hall was dingy and unimpressive...In 1934 a Harvard degree was no guarantee of a job and when Professor Wells asked me to join him in “An investigation of the air of textile mills with special reference to the influence of artificial humidification”
[13] He was a veteran of World War One
[15]Wells 1934 On Airborne Infection: Droplets and Droplet Nuclei Study II:It appears, therefore, that transmission of infection through air may take one of two forms depending upon the size of the infected droplet.
[16] The experimental unit in which these studies were carried out includes a tuberculosis ward with 6 single rooms a carefully controlled and calibrated closed circuit ventilating system, and a large animal exposure chamber located in the exhaust duct of this system
[17] In 1934, Wells drew attention to the difference in behavior between droplets and droplet nuclei, and suggested that droplet nuclei might be of predominant importance in the spread of respiratory contagion (1). (Review written by Riley, his protege)
[18] Cretyl Mills was the one on the spot, feeding and caring for the guinea pigs, tuberculin testing all 150 in the exposure chamber every month, keeping all the records, and fending off people with complaints.
[19] 'Over a three-year period more than 100 guinea pigs became infected, thus demonstrating beyond question that the air of the tuberculosis ward contained infectious droplet nuclei"
[20] She subsequently came down with TB and was put to bed in the very hospital where she had carried the torch for airborne infection.
[22] For tuberculosis (TB), definitive experimental evidence of airborne transmission being necessary and sufficient to cause disease was provided in a series of guinea-pig experiments
[23] https://onlinelibrary.wiley.com/doi/full/10.1111/j.1600-0668.2007.00469.x Airborne infection applies to dried-out infectious droplet nuclei derived directly from droplets less than 100 lm, which remain suspended in the air for a long time and could be carried over long distances by the air current
[25] https://academic.oup.com/aje/article-abstract/20/3/611/280025?redirectedFrom=fulltext The second form may be called air-borne infection, and deals with dried infected droplet nuclei, derived directly from droplets less than a tenth millimeter diameter, depending primarily upon air for the buoyancy which keeps them suspended for long times and carries them long distances. Droplet infection may change into air-borne infection when larger drops settle, evaporate and are lifted into the air as dust.
[26] CDC: Most experts think that flu viruses spread mainly by droplets made when people with flu cough, sneeze or talk.
[27] This indicates that expelled particles carrying pathogens do not exclusively disperse by airborne or droplet transmission but avail of both methods simultaneously and current dichotomous infection control precautions should be updated to include measures to contain both modes of aerosolised transmission.
[28] The range of contamination of the droplets is largely determined by their size. However, major uncertainties on the drop size distributions persist. Here, we report direct observation of the physical mechanisms of droplet formation at the exit of the mouth during sneezing. Specifically, we use high-speed imaging to directly examine the fluid fragmentation at the exit of the mouths of healthy subjects.
[29] We designed and built a new sampler, called the G-II, that collects exhaled-breath particles that can be used in infectivity analyses.
[30] Finding infectious virus in 39% of fine-aerosol samples collected during 30 min of normal tidal breathing in a large community-based study of confirmed influenza infection clearly establishes that a significant fraction of influenza cases routinely shed infectious virus, not merely detectable RNA, into aerosol particles small enough to remain suspended in air and present a risk for airborne transmission.
[31] National Institute for Occupational Safety and Health aerosol samplers collected size-fractionated aerosols for 60 minutes at the mouth of the breathing manikin, beside the mouth, and at 3 other locations in the room. Total recovered virus was quantitated by quantitative polymerase chain reaction and infectivity was determined by the viral plaque assay and an enhanced infectivity assay."
[32] Infectious virus and viral RNA can be detected in both larger particles 45 mm and smaller particles o5 mm14–16. Experimental studies have demonstrated that influenza virus can remain infectious in small particle aerosols, and can transit across rooms
[33] Our results suggest that aerosol transmission is an important mode and possibly the predominant mode of influenza A virus transmission in households. Aerosol transmission was estimated to account for approximately half of all transmission events (in this particular study)
[34] Within 72 h 72% of the 54 people on the plane became ill with typical symptoms of influenza.
[35] Recognition of aerosol transmission of infectious agents: a commentary smallpox: “At least one well-documented hospital outbreak, involving 17 cases of smallpox, could only be explained by assuming the aerosol spread of the virus from the index case, over several floors.” measles: “two other outbreaks in outpatient clinics included retrospective airflow dynamics analysis, providing more evidence for the transmissibility of measles via the airborne route [28, 29].”
[37] although S. aureus is transmitted most frequently by the contact route, viral upper respiratory tract infection has been associated with increased dispersal of S. aureus from the nose into the air for a distance of 4 feet under both outbreak and experimental conditions and is known as the “cloud baby” and “cloud adult” phenomenon118-120.
[38] For certain other respiratory infectious agents, such as influenza 130, 131 and rhinovirus 104, and even some gastrointestinal viruses (e.g., norovirus 132 and rotavirus 133 ) there is some evidence that the pathogen may be transmitted via small-particle aerosols, under natural and experimental conditions. Such transmission has occurred over distances longer than 3 feet but within a defined airspace (e.g., patient room), suggesting that it is unlikely that these agents remain viable on air currents that travel long distances.
[39] Polio is spread by the fecal-oral route. The virus can be found in bowel movements (feces) and spread through close contact with an infected person via small amounts of feces on unwashed hands. The virus can be found in the air after someone who is infected with polio coughs or sneezes and can be inhaled. From the CDC: Poliovirus only infects people. It enters the body through the mouth and spreads through: Contact with the feces (poop) of an infected person; Droplets from a sneeze or cough of an infected person (less common).
[40] Roseola is spread when a child breathes in droplets that contain the virus after an infected person coughs, sneezes, talks, or laughs but it does seem clear that close contact is required for transmission
[42] The sampling was conducted between February 17 and March 2, 2020 - see Fig 1. Epidemic curve of confirmed cases in China
[43] Thirty-five aerosol samples of three different types (total suspended particle, size segregated and deposition aerosol) were collected in Patient Areas (PAA) and Medical Staff Areas (MSA) of Renmin Hospital of Wuhan University (Renmin) and Wuchang Fangcang Field Hospital (Fangcang), and Public Areas (PUA) in Wuhan,
[44] Aerosol samples of total suspended particles (TSP) with no upper size limit to quantify RNA concentration of SARSCoV-2 aerosol;
[45] Presence of genetic material for influenza doesn’t translate to presence of viable virus: Numerous studies have shown the emission of influenza RNA from the exhaled breath of naturally influenza-infected human subjects [62,63,64,65,66] and have detected influenza RNA in environmental air [67,68,69]. More recently, some of these studies have shown the absence of [70], or significantly reduced numbers of viable viruses in air-samples with high influenza RNA levels (as tested by PCR) [66, 71, 72].
[46] E.g. This study found viability in aerosols https://www.nejm.org/doi/full/10.1056/NEJMc2004973 SARS-CoV-2 remained viable in aerosols throughout the duration of our experiment (3 hours), with a reduction in infectious titer from 103.5 to 102.7 TCID50 per liter of air…. The titer of viable virus is expressed as TCID50 per milliliter of collection medium. All samples were quantified by end-point titration on Vero E6 cells.
[47] Renmin Hospital of Wuhan University, designated for treatment of severe symptom COVID19 patient during the disease outbreak and the Wuchang Fangcang Field Hospital, one of
the first temporary hospitals which was renovated from an indoor sports stadium to
quarantine and treat mildly symptom patients, and outdoor public areas in Wuhan during the
coronavirus outbreak.
[48] The ICU, CCU and ward room in PAA of Renmin Hospital had negative test results. Fangcang Hospital workstations in different zones had low concentrations (1-9 copies m-3) of SARS-CoV-2 aerosol." And see Table 1
[49] We collected 545 specimens from 22 patients, including 209 pharyngeal swabs, 262 sputum samples, and 74 feces samples (Figure). In these patients, sputum and feces remained positive for SARS–CoV2 on RT-qPCR up to 39 and 13 days, respectively, after the obtained pharyngeal samples were negative
[50] Our results provide evidence for gastrointestinal infection of SARS-CoV-2, highlighting its potential fecal-oral transmission route
[51] Importantly, the live virus was detected in feces, implying that SARS-CoV-2 may be transmitted by the fecal route.
[54]polio: “aerosols generated by the flushing of the toilet resulted in the spread of the viral contamination to the air as well as to other surfaces in the washroom”
[55] This study also recorded an elevated airborne SARS-CoV-2 concentration inside the patient mobile toilet of Fangcang Hospital. This may come from either the patient's breath or the aerosolization of the virus-laden aerosol from patient’s faeces or urine during use
[56] We actually confirmed with the hospital authorities and the medical staff inside the Fangcang hospitals were all negative from record. We cross checked on this [Email with Dr Zhi Ning]
[57] https://www.nejm.org/doi/full/10.1056/NEJMc2004973 Our results indicate that aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days. See figure 1, "aerosol" data
[59] Human pathogenic coronaviruses (severe acute respiratory syndrome coronavirus [SARS-CoV] and SARSCoV-2) bind to their target cells through angiotensin-converting enzyme 2 (ACE2), which is expressed by epithelial cells of the lung, intestine, kidney, and blood vessels
[60] We show that SARS-CoV-2 S uses ACE2 to enter cells
[61] small chance could get in through eyes: Although we suspect the incidence of SARS-COV-2 infection through the ocular surface is extremely low, the nosocomial infection of SARS-CoV-2 through the eyes after occupational exposure is a potential route
[63] In December 2019, a novel coronavirus (CoV) epidemic, caused by the severe acute respiratory syndrome coronavirus – 2 (SARS-CoV-2) emerged from China. This virus causes the coronavirus disease 2019 (COVID-19). Since then, there have been anecdotal reports of ocular infection.
[64] https://www.ncbi.nlm.nih.gov/pubmed/25416753 infected people with influenza: “An optimal dose of 10^7 tissue culture infectious dose 50 was reached that caused mild to moderate influenza disease in 69% of individuals with mean viral shedding for 4–5 days and significant rises in convalescent influenza antibody titers.”
[65] https://onlinelibrary.wiley.com/doi/full/10.1111/j.1539-6924.2010.01427.x (SARS paper again)- the higher the dose the greater percentage of mice getting sick, according to this study “The does of SARS‐CoV corresponding to 10% and 50% responses (illness) were estimated at 43 and 280 PFU,”
[66] For SARS, one study found that you need hundreds of viral particles to make mice sick.” Citation: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1539-6924.2010.01427.x "The does of SARS‐CoV corresponding to 10% and 50% responses (illness) were estimated at 43 and 280 PFU, respectively." So 50% of mice got sick with 280 "plaque forming units". You may need more than 1 virus to form a plaque, so it's at least 280 viral particles.
[67] 3 patients: “ All air samples were negative.” https://jamanetwork.com/journals/jama/fullarticle/2762692
[69] Air sampling of two COVID-19 patients (both day 5 of symptoms) detected SARS-CoV-2 PCR52 positive particles of sizes >4 µm and 1-4 µm. One was negative. https://www.medrxiv.org/content/10.1101/2020.03.29.20046557v1.full.pdf
[70] A similar phenomenon was observed with rhinovirus; the probability of detecting airborne picornavirus RNA in office buildings was directly correlated with the carbon dioxide (CO2) content of the air, which is in turn inversely related to ventilation with fresh outside air [58];
[71] “While the viral load of the first confirmed case was 3.3 x 106 copies per mL in the pooled nasopharyngeal and throat swab and 5.9 x 106 copies per mL in saliva, respectively, on the day of environmental sample, the air samples were all undetectable for SARS-CoV-2 RNA when the patients were performing 4 different manoeuvres (normal breathing, deep breathing, speaking 1, 2, and 3 continuously, and coughing continuously) while putting on and putting off the surgical mask” https://www.cambridge.org/core/services/aop-cambridge-core/content/view/52513ACC56587859F9C601DC747EB6EC/S0899823X20000586a.pdf/escalating_infection_control_response_to_the_rapidly_evolving_epidemiology_of_the_coronavirus_disease_2019_covid19_due_to_sarscov2_in_hong_kong.pdf
[72] e.g.COVID-19 is thought to spread mainly through close contact from person-to-person in respiratory droplets from someone who is infected. People who are infected often have symptoms of illness. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-covid-spreads.html
[73] Acoustic coordination by allied male dolphins in a cooperative context | Proceedings of the Royal Society B: Biological Sciences
[74] Motor synchrony has been shown to play an important role in promoting cooperation between these allied dolphins, purportedly acting as a signal of alliance unity
[75] Males mediate alliance relationships with gentle contact behaviours such as petting, but synchrony also plays an important role in affiliative interactions. In
[76] Here we report that synchronous surfacing in male bottlenose dolphins is associated with alliance membership and that synchrony between members of cooperating alliances is more common during social behaviour than during nonsocial behaviour especially during bouts of ‘intense’ social behaviour (e.g. mounting, displays, chasing) with female consorts.
[77] given the rate at which these pops are produced (x̄ = 10 pops per s, approx. 600 beats per min (BPM)
[78] Recordings courtesy of Dr. Stephanie King, corresponding author of this study
[79] These strong alliance relationships can last for decades and are critical to each male's reproductive success