Aerosol and surface stability of HCoV-19 compared to SARS-CoV-1 [pdf]

https://www.medrxiv.org/content/10.1101/2020.03.09.20033217v1

by mhb • 6 years ago

78 43 6 years ago

aaronscott• 6 years ago

From the paper: "Our results indicate that aerosol and fomite transmission of HCoV-19 is plausible, as the virus can remain viable in aerosols for multiple hours and on surfaces up to days."

This partially explains how quickly this virus spreads, and why such incredible measures are required to stop the spread.

nostromo3• 6 years ago

and why such incredible measures are required to stop the spread.

Since we're learning that the fatality rate is much lower than SARS, as was feared early on, and that it's much more mild of an illness -- and also that it's highly contagious and already widespread -- it strikes me that the opposite is true.

We should do everything we can to protect the elderly and ill, but a disease that is so mild that 85% of people over 80 still survive it, it doesn't strike me as something worth tanking the global economy over. If you're middle-aged or younger and you drive to work, travel internationally, drink alcohol, etc., you've taken similar risks as COVID-19 poses to you.

This is incredibly unpopular on HN, and I'm ok with that. Holing everyone up in their apartments for the next year would put almost everyone reading this out of a job, many without housing, and without healthcare. This is a "keep calm, wash your hands, and carry on" moment, and we're failing.

eloff• 6 years ago

I think we have different definitions of mild. Something that kills 1% of healthy middle aged people is quite scary.

d4mi3n• 6 years ago

I'd still be concerned about further mutation. With something as virulent as HCoV-19, even a minor increase in morbidity rates could be catastrophic.

Even without high morbidity rates, a survival rate of 85% without treatment is still horrific in scenarios where local healthcare systems become overwhelmed. Reading accounts of just that happening in Italy is chilling.

ardit332• 6 years ago

There are reports, that plenty of those "80%" mild cases have pneumonia and permanent lung scaring (aka, you will never be able to play intense sports), even though they don't end up in a tube/forced oxygenation....

Sorry, I'd rather take a 2 months economy hit, than a long term burn.... which will cause a longer term economic problem as well.

cjbprime• 6 years ago

Your country (whichever one it is) doesn't have enough ICU beds for 10% of people over 70 -- it probably has orders of magnitude fewer available beds -- and note that people who don't die can still end up in hospital for weeks and requiring a respirator, increasing that percentage of beds required.

My amateur understanding is that accelerated contagion of COVID-19 will destroy your country's health infrastructure, and then many people who don't have COVID-19 will start dying too because healthcare can't reach them. That's why delaying infection is so valuable. It's not just about the direct symptoms that most people get.

astronautjones• 6 years ago

We should do everything we can to protect the elderly and ill, but a disease that is so mild that 85% of people over 80 still survive it, it doesn't strike me as something worth tanking the global economy over. If you're middle-aged or younger and you drive to work, travel internationally, drink alcohol, etc., you've taken similar risks as COVID-19 poses to you.

You're wrong, though. Regardless of how dismissive you want to be about people getting the virus, they are going to have symptoms that make them seek treatment. the system cannot accommodate large numbers of people seeking treatment.

No one is going to "keep calm" when they feel severely ill, they're going to rightly seek help from doctors. The crisis is when lots of people seek that help at once. We are trying to prevent that and it's worth it!

If the US economy takes a shit, it's going to be because the government is offering no financial help whatsoever to the people who are going to be destitute when they miss work.

slg• 6 years ago

I don't understand how this can be true and the R0 is somewhere in the 2-4 range as some are reporting. It seems like it would be incredibly easy to spread if someone can go days without knowing they have the virus and the virus can live for days on any surface they touch.

RandallBrown• 6 years ago

You typically need more than just 1 virus in your system to get infected. Your immune system will do a good job of taking care of the 1.

The study just says they were able to detect live viruses after that amount of time, not that they would definitely infect you. It's likely that the odds of infection are very low before that 3 hour mark.

Unless I'm misreading the study.

etiam• 6 years ago

If something has to give, it seems to me like a strong possibility it's the R0 range estimate. Authorities, and to some extent media, in my country have been very tenacious in trying to reassure people. Often up to the point of outright disinformation. At the start of this week the pacifier statement in vogue was that the mortality rate estimate is inflated because the severe cases are those who self-present for care. and thus testing. so if one counts all the cases, including the undetected ones, a much smaller fraction are lethal.

Well, that one's true, but the flip side of that, which nobody here has wanted to address so far, is that to the extent the transmissibility is calculated based on corresponding data, that estimate is going to be deficient instead, because it's failing to include some of the contagion that resulted in cases that went undetected. Hopefully the people making the estimates know better than that because of other data sources, but the main one I can think of (maybe aside of South Korea's broad biochemical testing, which may be a relatively unbiased sample according to my perception?) is contact tracing of confirmed cases. And I think it's downright likely that at least our contact tracers would miss fomite transmission and persistent aerosol transmission until now, because the party line touted here, at least officially, is "you get the disease though close contact over a long time with someone who is sick" lately expanded to include "or if somebody coughs or sneezes at you" (emphasis mine).

The other thing I can think of to somewhat reconcile the observations is even if the virus has a high durability in the environment, the total transmission process would be contingent on other factors too, one of which is the dose needed to get an infection going.

I have a life science background, but not specific expertise in this area. Would appreciate if someone has good clarifications to share about how accurate the transmissibility estimates are likely to be and why.

dogma11382• 6 years ago

Because while you can be an asymptomatic carrier it doesn’t you are very infectious at that point, viral shedding levels and coughing play a bit role in this.

Also if the R0 value is much higher than the current estimate it’s good because it would also means it has a much lower mortality rate and overall much less lower severe infection rate than what we currently can estimate.

R0 values are very hard to calculate for novel viruses you usually only can figure it out after multiple outbreaks where you can account and control for environmental and societal conditions.

akiselev• 6 years ago

The measles virus is much better studied and it behaves like the aerosol described. It's contagious to the point where any sort of contact in an enclosed space is practically guaranteed to infect anyone who isn't immunized from a vaccine or previous exposure (and sometimes even then).

Based on the numbers South Korea has put out for numbers of infected vs tested and the extensive contact tracing they've done, it doesn't seem that this virus quite reaches that level of infectiousness. I think there's more to the story, like HCoV-19 may have a half life long enough for experiments to detect on surfaces and in an aerosol, but short enough that it doesn't present enough of a viral load to infect anyone relatively quickly.

altarius• 6 years ago

The only generally applicable information form the paper is the viral half-life in aerosols/on surfaces and comparing it to SARS-COV1.

This won't help in determining how long to quarantine packages unless someone finds out what the typical viral transfer is e.g. when sneezing or when handling a package with contaminated hands - and how many/few viral particles "ingested" may cause an infection.

I don't think one can simply conclude at all that "viruses will survive X days on cardboard/steel/plastic" because viral particles go through an exponential decay in the environment -- so more particles == more time to inactivate all the viruses, and the reverse.

As far as I understand it, there's no predetermined "viable lifetime" (a sort of biologic clock and death) of a virus, the environment will just eventually destroy it and that point seems essentially random for an individual viral particle with different probability distributions on different surfaces.

So if you start with a viral load that is higher, you will be able to detect viable viruses longer.

So these numbers, e.g. detectable for 3 hours in aerosol don't mean anything unless the average human sneeze excretes as many viral particles as a "3-jet Collison nebulizer". If we excrete more than more viral particles remain viable longer and the detection threshold is reached later. If less, than those 3 hours don't apply.

RichardHeart2• 6 years ago

COVID19 lives for 3 hours in air. 2-3 days on stainless steel and plastic. Only 4 hours on copper, which is why all door handles should be copper! Other anti-viral and bacterial materials are available as well.

heretoo• 6 years ago

or everyone should wear copper gloves

Someone1234• 6 years ago

How would that help? A gloved hand can still pick up surface viral load and transfer it to the face. The nice thing about anti-viral surfaces like copper is that it reduces surface virus, a glove doesn't do that.

GuB-422• 6 years ago

Or gloves filled with mercury...

Obviously, that's a joke but it is probably not as bad as you might think. Liquid elemental mercury is relatively harmless. Compare to mercury vapor, which is bad, and organic mercury, which is worse than bad.

scrumbledober• 6 years ago

probably bronze for durability but yes this is why a huge amount of door knobs are already made out of bronze. (they also look real cool when they wear with age)

sam_lowry_• 6 years ago

Gold or silver

GloriousKoji• 6 years ago

Copper is probably the best out of the available materials given availability, price, human toxicity, etc.

https://en.wikipedia.org/wiki/Oligodynamic_effect

davidw• 6 years ago

I wonder what - if anything - post offices / delivery services are doing about this stuff? A lot of people hunkered down at home are going to use those to order things.

btown• 6 years ago

Not to mention that of all industries to pressure their workers not to take time off, delivery and postal services will see record demand, and so it's more likely than the general population that a package handler might be infected...

devit• 6 years ago

People should not handle any package for at least 3 days after reception assuming this paper is correct (unless they manually disinfect it).

EDIT: actually the paper doesn't seem to conclude that 3 days is enough, and instead than an unknown number of days, but at least 3, is required, at least relative to their detection method

erichurkman• 6 years ago

Can you effectively disinfect porous materials like paper and cardboard?

ardit332• 6 years ago

So, someone sick goes into an elevator/bus/small places, they cough, and get on. The guy coming 5 mins later, having no clue, might get infected....

And while 'wash your hand', helps some, it is mostly just a way to make people feel control, as that seems not to be the main vector of transmission. This explain how quickly many people get it.....

This is a crude analogy, but: if you are close enough to someone and you would probably noticed if they 'farted', then there is a good chance that you would get some potential covid-19 particles if their coughed it out.....

34679• 6 years ago

Someone sick walks into a building with central air/heating without HEPA filtration or sterilization, walk past a return vent, and the virus gets sucked in and sent out throughout the whole building.

GuB-422• 6 years ago

Don't forget the "viable on surfaces up to days" part.

Someone coughs on a doorknob, hours later, you touch the doorknob, virus goes on your hand, you touch your face, you get infected.

Even if you don't touch your face, your dirty hands spread the virus everywhere, including on food and to other people.

And even if touch isn't the main vector, it is better than nothing. Remember that the goal is to make the rate of transmissions less than 1, so if washing hands help us go down from 1.1 to 0.9, even if isn't that much of a difference, it is all we need to beat the virus.

csytan• 6 years ago

From the paper:

Virus stability in aerosols was determined as described previously at 65% relative humidity (RH) and 21-23°C. In short, aerosols (<5 µm) containing HCoV-19 (105.25 TCID50/mL) or SARS-CoV-1 (106.75-7 TCID50/mL) were generated using a 3-jet Collison nebulizer and fed into a Goldberg drum to create an aerosolized environment. Aerosols were maintained in the Goldberg drum and samples were collected at 0, 30, 60, 120 and 180 minutes post-aerosolization on a 47mm gelatin filter (Sartorius). Filters were dissolved in 10 mL of DMEM containing 10% FBS. Three replicate experiments were performed.

logjammin2• 6 years ago

Thanks for posting this. As someone in public health research, I really appreciate being able to get as close as possible to empirical findings about corona. It helps me deal both rationally and emotionally with the crisis. Obviously "it's just a preprint", but this is great to have -- leagues better than a watered-down and panicked-up version from cross-eyed cable news hosts.

I've found that the major scientific and biomedical research journals - the BMJ, the Lancet, the NEJM, JAMA, Science, Nature - collectively have some of the best stuff on coronavirus out there. It's not as fast as the news, but it's a hell of a lot more rigorous.

abruzzi• 6 years ago

The slightly tangential question I had was, OK, a potential active lifespan of 2-3 hours in aerosol form, but in a normal environment, how long is it likely to remain in aerosol form before settling on a surface, and in what environments is it likely to remain airborne for 2-3 hours?

logjammin2• 6 years ago

That's a good question, no doubt. A related one I had was (and maybe I missed this), but what's the "dose" of virus one needs to get infected? In the discussion of decay / half life of the virus on surfaces and in the air, I wondered about this. It's one thing if the virus can hang around for three hours and infect you at any time, and another thing if it's in the air for three hours but decays at ____ rate and can only infect for 1 hour.

Amarok• 6 years ago

TCID50 gives you information on infectivity. Not as good as LD50 though https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4861875/

RichardHeart2• 6 years ago

Here's how well copper as a surface kills viruses and bacteria: https://en.wikipedia.org/wiki/Antimicrobial_properties_of_co...

pteiavn• 6 years ago

"In short, aerosols (<5 μ m) containing HCoV-19 (105.25 69 TCID50/mL) or SARS-CoV-1 (106.75-7 TCID50/mL) were generated using a 3-jet Collison nebulizer and fed into a Goldberg drum to create an aerosolized environment. Aerosols were maintained in the Goldberg drum and samples were collected at 0, 30, 60, 120 and 180 minutes post-aerosolization on a 47mm gelatin filter (Sartorius). Filters were dissolved in 10 mL of DMEM containing 10% FBS. Three replicate experiments were performed."

I looked up "Goldberg drum" and found this https://www.researchgate.net/figure/Aerosol-apparatus-A-40-L... which looks pretty small. It would dissipate a lot more in a room, and even more outdoors. How can we account for the effects of dissipation?

Aerosol and surface stability of HCoV-19 compared to SARS-CoV-1 [pdf]

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