TIL: Sneezes and "its payload of pathogen-bearing droplets of all sizes can travel 23 to 27 feet (7-8 m)."
Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19 https://t.co/JXar76Euwr
Although such social distancing strategies are critical in the current time of pandemic, it may seem surprising that the current understanding of the routes of host-to-host transmission in respiratory infectious diseases are predicated on a model of disease transmission developed in the 1930s that, by modern standards, seems overly simplified. Implementing public health recommendations based on these older models may limit the effectiveness of the proposed interventions....
Given various combinations of an individual patient’s physiology and environmental conditions, such as humidity and temperature, the gas cloud and its payload of pathogen-bearing droplets of all sizes can travel 23 to 27 feet (7-8 m).
This is published in JAMA; have the WHO found differently?
You should contribute only high-quality information. We require that users submit reliable, fact-based information to the subreddit and provide an English translation for an article in the comments if necessary. There are many places online to discuss conspiracies and speculate. We ask you not to do so here. (More Information)
These new findings, along with the asymptomatic nature of the coronavirus (1) and its ability to remain active on surfaces (2), could be an explanation for its widespread infection
Turbulent Gas Clouds and Respiratory Pathogen Emissions
Potential implications for reducing transmission of COVID-19
The dichotomy of large vs small droplets remains at the core of the classification systems of routes of respiratory disease transmission adopted by the World Health Organization and other agencies, such as the Centers for Disease Control and Prevention. These classification systems employ various arbitrary droplet diameter cutoffs, from 5 to 10 μm, to categorize host-to-host transmission as droplets or aerosol routes.1 Such dichotomies continue to underly current risk management, major recommendations, and allocation of resources for response management associated with infection control, including for COVID-19. ¨Even when maximum containment policies were enforced, the rapid international spread of COVID-19 suggests that using arbitrary droplet size cutoffs may not accurately reflect what actually occurs with respiratory emissions, possibly contributing to the ineffectiveness of some procedures used to limit the spread of respiratory disease.
A 2020 report from China demonstrated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus particles could be found in the ventilation systems in hospital rooms of patients with COVID-19
The protective efficacy of N95 masks depends on their ability to filter incoming air from aerosolized droplet nuclei. However, these masks are only designed for a certain range of environmental and local conditions and a limited duration of usage. Mask efficacy as source control depends on the ability of the mask to trap or alter the high-momentum gas cloud emission with its pathogenic payload.Peak exhalation speeds can reach up to 33 to 100 feet per second (10-30 m/s), creating a cloud that can span approximately 23 to 27 feet (7-8 m). Protective and source control masks, as well as other protective equipment, should have the ability to repeatedly withstand the kind of high-momentum multiphase turbulent gas cloud that may be ejected during a sneeze or a cough and the exposure from them.Currently used surgical and N95 masks are not tested for these potential characteristics of respiratory emissions
Welcome to r/science! Our team of 1,500+ moderators will remove comments if they are jokes, anecdotes, memes, off-topic or medical advice (rules). We encourage respectful discussion about the science of the post.
But oh no, don’t you see it rides on water and is therefore water droplet only. Haha, idiots claiming it is aerosolized. I am so smart because I only use info from the WHO and CCP. It can’t stay in the air because it’s not airborne. Therefore I am right.
It would be interesting to consider directionality in this analysis. A sneeze going 7-8m forward is different than it going 7-8m in all directions. They do hypothesize that indoor climate control can have a big impact though, which makes sense.
I think there’s little point or utility to this article. It just names areas of future study for fluid dynamicists. The fact that a cough or sneeze can go farther than 6 feet shouldn’t be a surprise to anyone who thinks about respiratory diseases.
It's a beginning point in understand the means of travel of viruses. No one is thinking seriously about actually containing individual sneeze output. If we do that we can, in theory, stop the virus.
A though experiment - let's say every time someone coughed/sneezed they put a big plastic bag around their nose/mouth and all of the output/cloud was captured in that bag, and that bag was tied up and thrown away; in theory, you would remove the virus from the environment (from this transmission method); the droplets would not land on surfaces (fomites); it would not hang in the air waiting for someone else to breathe in. This would greatly reduce transmission.
Wearing masks help a bit, but obviously aren't full proof.
What comes out when we sneeze is "mucosalivary droplets" -- ie it is basically mucus and saliva, but in "aersolized" and "dropletized" form. We would never accept ingesting a stranger's mucus or saliva, and health workers treat those fluids very carefully (when taking samples for testing, just as they would treat urine, sperm, etc); yet sick people walk right into doctor's offices and ER waiting rooms and can expel their mucus and saliva right into the air, and this is accepted because it's just always how its been. We need to start thinking differently about this.
I have inventions that could solve for this but I doubt I have the resources to bring them to fruition.
[imgur] is not a scientific source and cannot easily be verified by other users. Please use sources according to [Rule 2](https://www.reddit.com/r/COVID19/about/rules/) instead. Thanks for keeping /r/COVID19 evidence-based!
*I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/COVID19) if you have any questions or concerns.*
The videos are slowed down. The first 2 are less than a half a second in real time. The last one is 6 seconds.
Still not incredible news but don’t get the impression that such a high concentration of exhaled air isn’t prone to diffusion like any other substance.
> nightmare fuel
Yep, not showing this to my already-germophobic wife.
Since there are indications the density of viral load matters, I wonder what the falloff rate is at the edges and over time. IIRC a study posted last week had density measurements taken in an actual hospital environment (in Nebraska I think). Another study, also posted last week I think, indicated that not all detectable CV19 is necessarily infectable CV19.
More distance or more protection are always better but the dynamics are complex and we need more info to balance probability and practicality. I'd love to see this expanded into a practical study in environments like hospitals, offices and stores showing the incidence of particles sufficient to cause infection as a falloff per square of the distance and time.
The high frequency and viral loads found in hospital ERs and ICUs dictate maximum precaution. However, if doubling social distancing from 6 feet to 12 feet in a retail store environment only decreases the probability of actual infection slightly, it may not be worth it as it would make it impossible to navigate a typical grocery store. Yesterday I was getting groceries for an elderly family member and everyone at the grocery was respectfully navigating around in virtual six-foot bubbles and it was already at the edge of practicality. I started pondering, "If almost all the at-risk people and the currently symptomatic people are staying home (and most seem to be, viral social media reports aside), then the odds of being infected during the three seconds two people are passing in a supermarket aisle is probably pretty darn low."
Quick question, I see all of this viral load talk. How could anyone possibly know what someone’s initial viral load was at the time of infection? Can you trace back to see that somehow? To me it seems more likely that when viral load is discussed, it is speaking of the idea that if someone currently has a high viral load, that is bad, which seems obvious. I would love to know the answer to this, and I know you might not know but I thought I would ask since you mentioned it. Thanks!
There was a German study where they swabbed patients every day and tracked viral load but I can't find the link. Maybe someone else can link it.
Here's [a CDC study](https://www.cdc.gov/mmwr/volumes/69/wr/mm6909e1.htm) on incidence of CV19 infectious transmission. I also remember seeing a Korean study of households where they tracked the likelihood of infection, which I also can't find (too many studies, not enough brain). From some study I read, the notion stuck in my brain that the chances of getting CV19 from someone you live or work with is dramatically higher than getting it from someone you pass on the street or in a store, which makes sense but I continue to see people act the opposite way.
You can't know, but you can know a person surrounded by 6 symptomatic people (like healthcare workers are) are going to be exposed to more of the virus than someone who was exposed during a checkout at the grocery store with an asymptomatic spreader.
I get that, but I keep seeing that studies say the higher the initial viral load, the worse the outcome or something similar. Are they following healthcare workers that they know were highly exposed? It seems that they wouldn’t have enough data to look at deaths and then figure out if they got it from touching a key pad or if someone on deaths door coughed straight down their throat.
Prof. Drosten speculated that severe cases might result from deep inhalation of viral load and skipping the "mild phase". He was discussing the hypothesis that the body needs some time to build anti bodies, that could fight the lung stage of CV19.
Virus replicates exponentially in the body. I am no epidemiologist. However, it would seem intuitive that the virus gets a head start on its exponential growth curve. Anti body production would have to play catch up in this race condition.
Please do not quote me on any of this. But I too have heard what you are inquiring and this is how I made sense of it. It's probably false to think of vaccines that way.
**Edit** /u/Hai_Wayland is [confirming the hypothesis that i seem to recall and cites a study](https://www.reddit.com/r/COVID19/comments/fr70j1/turbulent_gas_clouds_and_respiratory_pathogen/fluoqkd/) below.
They measure the viral load in the swabs taken during tests. Viral load is measured on a logarithmic scale, so "high" viral load means orders of magnitude more than "low" viral load.
The idea is that if there's more in your nose or in your throat, the initial amount of virus that gets into your lungs is higher, sort of "surprising" the immune system which doesn't get enough time to react to it. That's why higher initial viral load could result in higher likelihood of a severe case.
EDIT: Here's the study - "Viral dynamics in mild and severe cases of COVID-19"
That's still not fully proven, though. Figure B is missing early onset data for nearly every severe case. It's plausible that severe cases and mild cases had a similar initial dose, but that mild cases were able to mount an effective immune response while severe cases weren't.
Not all progression in the study showed improvement. A couple of mild cases showed growing viral loads at different stages before reverting back to smaller loads. And there's less of a clear trend towards clearance in the severe population: more flat days at the start.
When you consider that age is a highly correlated variable, there's very likely more to this than is presented here.
I would say for a healthcare worker, hospitals are (or will be) so swamped they are nearly guaranteed exposure. Put yourself in the shoes of a nurse in NYC, out of PPE, running from patient to patient all day for dozens of patients, managing and handling god knows how many bodily fluids on literally everything, sheets, IV lines, respirometers, etc.
I imagine healthcare workers know exactly what they're getting into, and they have been going in willingly or some are choosing to stay home. Not all have the privilege to speak up without consequences and I've read so many stories about docs being fired for it. It's not a good system. 😞
I was walking the other day and realized I could strongly smell the lady’s cigarette from half a block and across the street. If there’s sickness in the exhalation, that shit reached me. 6 foot ain’t shit to air.
Also, pretty sure today is day 1 of me existing after having covid. First day in 2 weeks it doesn’t feel like there’s a rubber band around my heart or little dudes with vacuum hoses scraping my throat and throwing it all into my lungs. Pretty excited about this!
Edit: any idea where to get either a covid test or antibody test in Los Angeles? I’d like to go get a temporary job somewhere...
Just because you could smell tobacco smoke from 100 feet away does NOT mean viral particles travel 100 feet. Similarly, one can smell wildfire smoke from fires hundreds of miles away. That doesn't mean that someone 100 miles downwind of NYC or Wuhan is going to catch Covid by walking out on their back patio and taking a breath of outdoor air.
True. But the video, if I'm viewing it correctly, does show that the expelled "cloud" can travel upwards of 26 ft, which is much farther than I've heard anyone talk about, and wayyy farther than the 6 ft recommended by CDC, WHO, etc.
True however you also have to consider that droplets, where a virus can remain infectious, need to have a certain size. If they are too small, they dry out (vaporise) quickly and destroy the virus. However, only the small droplets reach the longest distance, since the can float the longest in the air. The larger droplets, where the virus can survive the longest, are dropping much quicker to the ground, since the can't float that the long in the air. This explanation is based on the German Virologist Prof. Drosten.
Since, as you stated, virus survives longest in droplets reaching the ground, isn’t it likely we can carry the virus on our footwear? Should we don gloves to remove our shoes? Not asking a silly question but honestly wondering.
Yes, it is definitely possible. I think the best practice is to keep your home sterile by not wearing outdoors shoes in your house, and by washing your hands after touching shoes you wore outside in the past few days. If you’re going to stores, designate one pair of shoes and keep them far as possible away from the rest of your living space.
Yes, that's a very good practice in general. (my area has unfortunately a lot of dog shit on sidewalks. So there is a good chance, I get small but significant amount of feces on my shoes as well.) It also good practice to use the same clothes (e.g. Jacket and trousers) for grocery shopping but for nothing else and keep them separate from all the other clothes.
I didn't want to disprove anything here. I just wanted to make you aware that there has to be an additional dimension to be considered here. And there might be more, which we are both not aware of. So, just because this "cloud" travels far, doesn't imply that the infectiousness of a virus carried within that cloud remains the same over time. Hence, it's not wise to jump too quickly to conclusion here. On the other hand, it can't hurt to take proper precautions.
Also, you say they "dry out" quickly. That depends also on humidity and temperature.
At the end of the day, this is essentially mucus and saliva that goes from one person to others, which if you think about it is really disgusting, even sans virus. But since it is in droplet form we don't take it as serious as if it were a glob of mucus or saliva. Especially medical setting (doctor waiting room for ex, hospital, nursing homes, etc) this should be taken much more seriously.
This is a very solvable problem. It's very strange to me that no one takes it serious. At least Asians's sort of take it serious, hence the mass adoption of masks, but there are even better ways to control the droplets. I have the inventions in my head and am thinking about working on this, but I'd really need some medical experts to work with.
The weather condition are indeed very important on the propagation of this cloud and for the change of infectiousness of the virus within the cloud but unfortunately also very complex to model.
When it comes to wearing a mask for normal people, it appears that's more effect to prevent spreading the virus, if the infected person is wearing one than if a healthy person is wearing one. This also means, if an asymptomatic person is wearing one out of habite, this certainly appears useful. The problem is that the aren't enough masks for everyone at the moment and the medical personal need them the most. Hence, it may harm the health system of a country, if normal people start buying and using (excessively/inappropriately) face masks. So, if you have an unused mask at home, it might be more useful to donate it to a hospital than using it for yourself, assuming that you are still healthy.
The title of your post does not contain the source's original title [Rule 3]. Please use a title in accordance with our rule:
"Include a source's original title in a post title whenever applicable. Providing additional objective context, such as the authors and the published journal, is encouraged. An editorialized, sensationalized, misleading, or factually-inaccurate title will result in a post's removal."
A 2020 report from China demonstrated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus particles could be found in the ventilation systems in hospital rooms of patients with COVID-19.5 Finding virus particles in these systems is more consistent with the turbulent gas cloud hypothesis of disease transmission than the dichotomous model because it explains how viable virus particles can travel long distances from patients.