Preprint: low temp, extreme relative humidity - Printable Version
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Preprint: low temp, extreme relative humidity - magnus - 10-26-2020
Preprint out on a study that determined low temperature and extreme relative humidity allowed the virus to survive longer.
[Tweet]https://twitter.com/dylanhmorris/status/1317452511624790017?s=20[/tweet]
The abstract says 10C and 40 RH extended the half life to 24 hours. Is 40 RH extreme though?
10C also doesn't seem that cold...to most Americans this fall.
RE: Preprint: low temp, extreme relative humidity - M T - 10-26-2020
I'm no fan of posted tweets rather than links to the actual substance.
The abstract is here:
https://www.biorxiv.org/content/10.1101/2020.10.16.341883v1
with a link to the full paper.
When I see someone describing a "notable U-shaped curves" from 3 points, I have to wonder.....
None of the temperatures or relative humidity levels are "extreme". (Where I live, in the last week, our temperature has been above 27C and below 10C. 36 hours ago, our RH was 96%, but RH hasn't been reached 40% for the last 21 hours, reaching down to 17%.)
They used 3 samples at each of the 9 environmental conditions at the cross product of 10, 22, and 27 degrees C and 40, 65, and 85% RH.
All their samples were in one medium.
Of the 9 environmental conditions, they measured the level of virus at two time points for 4 conditions, at 3 time points for 2 conditions, at 4 time points for 1, at 5 time points for 1, and 6 time point for 1.
When I looked at their extended data (using the measurements of others), they didn't include other studies I would have expected. (1(too recent), 2, 3, 4)
They theorize a model for the decay of the virus. Maybe they are right, maybe not. I was wondering how they accounted for 10x difference in half-lives at the same temperature & RH but different surfaces, as measured in other studies, and the much longer half-lives calculated in study #1 above. But I got disappointed in their data (incl. extended) and didn't dig as deep as would be necessary.
RE: Preprint: low temp, extreme relative humidity - M T - 11-05-2020
Since this was the latest thread about persistence of SARS-COV-2, I thought I'd post another Research Letter that I find worrisome.
This group tested the longevity of the virus on aluminum, glass, and polystyrene plastic, with and without Bovine Serum Albumin (BSA).
The BSA was to mimic the protein content within body fluids of the respiratory system.
They tested at the recommended indoor environment of 45-55% RH, 19-21º C.
Without BSA, the half-lives (Remember, the time for 99.9% reduction is 10x this number) were
A: Glass: 17 hours
B: Polystyrene plastic: > 96 hours (ie, 4 days).
C: AL: 2.5 hours
With BSA, ALL the half-lives were > 96 hours.
![[Image: 20-1788-F1.jpg]](https://wwwnc.cdc.gov/eid/images/20-1788-F1.jpg)
Even without BSA, these are much longer than the early study that set people's expectation:
An early study (40%RH 21-23º C) reported these half-lives (eyeballed from a graphic):
Aerosols: 1.1 hours
Copper: 1.5 hours
Cardboard: 0.5 hours
Stainless steel: 4 hours
Plastic: 7.5 hours
Another recent study (50% RH 20º C, in the dark) reported these half-lives
Stainless steel: 43 hours
Polymer note: 49.4 hours
Paper note: 65.8 hours
Glass: 45.6 hours
Cotton: 43.2 hours
Vinyl: 45.8 hours
It feels to me that there is more going on here than just ambient UV.
Considering that 54% of SCC cases are from unknown contacts, maybe fomites are playing a bigger role than the CDC currently acknowledges.
I know of a case last week in a food service that has me concerned about how many secondary infections could be from fomites from this one person. I believe that if you went to a eating establishment (indoors, outdoors, to-go), and a server, cashier, or cook got sick, or you go ot a grocery store where a cashier or stocker got sick, you wouldn't be informed. If you got sick, you'd be in that 54% with unknown contacts.
RE: Preprint: low temp, extreme relative humidity - Snorlax94 - 11-05-2020
(11-05-2020, 09:58 PM)M T Wrote: ...
It feels to me that there is more going on here than just ambient UV.
Considering that 54% of SCC cases are from unknown contacts, maybe fomites are playing a bigger role than the CDC currently acknowledges.
I know of a case last week in a food service that has me concerned about how many secondary infections could be from fomites from this one person. I believe that if you went to a eating establishment (indoors, outdoors, to-go), and a server, cashier, or cook got sick, or you go ot a grocery store where a cashier or stocker got sick, you wouldn't be informed. If you got sick, you'd be in that 54% with unknown contacts.
The 54% of SCC cases from unknown contacts and "community spread" are so concerning and maddeningly frustrating. So many of us were looking to contact tracing to get a handle on this thing. The cup half-full view is that maybe it takes a full cycle to get contact tracing down and we'll be prepared next time.
As for the speculation regarding fomites, I keep thinking back to that Korean call center study.
I think it was a 15 story building where they tested 1,145 contacts. The first case was on the 10th floor, but from then on, 97% of the confirmed cases were all on the 11th floor, and of those, almost all of them were in close range.
If fomites were such a formidable source of spread, I'd expect more of the infections to break out beyond the 11th floor, and to pass to co-workers on different floors and on the opposite side of the building.
And although I could be over-reliant on this one study, from a different country that may have very different practices (how often do employees go to break rooms, etc.), the contact tracing in the US has been so weak and inconclusive that I'd still probably trust studies like the S Korean one more. They had a contained system -- one building, and they jumped on it with a ton of investigators and testing. This leads me to believe we frequently have no idea where it came from not because the spread is from mystery fomites, but because our contact tracing is failing to uncover the contacts. Some day we'll know, but my guess right now is that many people are lying. By "always wears a mask", I suspect they mean except for the weekends when they go to 1-2 indoor house parties that they don't want to tell the contact tracers about. I believe there are *some* mystery cases of people who truly always wear masks and never mingle unnecessarily, but my guess is that the true rate is very, very low. Another possibility is that a fair chunk of of the mystery community spread is coming in the eyes. My impression is that a lot more people in Korea and China wear glasses, so maybe that is why their contact tracing and containment is so much more successful.
![[Image: 20-1274-F2.jpg]](https://wwwnc.cdc.gov/eid/images/20-1274-F2.jpg)
RE: Preprint: low temp, extreme relative humidity - Goose - 11-06-2020
(11-05-2020, 09:58 PM)M T Wrote: Considering that 54% of SCC cases are from unknown contacts, maybe fomites are playing a bigger role than the CDC currently acknowledges.Could be true. However, the 54% of the cases not being from known contacts is more easily explained by the fact that a total of 58% of the cases either name no contacts (do not cooperate) or cannot be reached (15%). I think that is a much bigger problem.
Quote:I know of a case last week in a food service that has me concerned about how many secondary infections could be from fomites from this one person. I believe that if you went to a eating establishment (indoors, outdoors, to-go), and a server, cashier, or cook got sick, or you go ot a grocery store where a cashier or stocker got sick, you wouldn't be informed. If you got sick, you'd be in that 54% with unknown contacts.Probably true you would not be contacted as a "close contact" unless you were known to have been served by the employee in question. It is unclear to me what would happen when you showed up sick. In "normal" times, effort would be expended figuring out where you got the disease, and the establishment with the positive case would come under scrutiny. An even better question that I have no answer for is if a person tests positive and names a contact who has previously tested positive but did not name the current person as a contact counted as a contact to a case? Clearly the subsequent case IS a contact to a case, but was not originally named as such.
RE: Preprint: low temp, extreme relative humidity - M T - 11-08-2020
(11-06-2020, 04:33 PM)Goose Wrote:(11-05-2020, 09:58 PM)M T Wrote: Considering that 54% of SCC cases are from unknown contacts, maybe fomites are playing a bigger role than the CDC currently acknowledges.
Could be true. However, the 54% of the cases not being from known contacts is more easily explained by the fact that a total of 58% of the cases either name no contacts (do not cooperate) or cannot be reached (15%). I think that is a much bigger problem.
No, that doesn't explain it. Maybe it is somewhat confirming that close contact is not responsible for even half the spread.
If person B gets COVID, 54% of the time they don't know ANY person A from whom they might have gotten the disease (that are known to have the disease by B or by the county) in the last 2+ weeks. Most likely they would know of whom they had close contact with. (Exceptions would include mass transit, gatherings (sports, political incl. voting in person) where they might have spent 15 minutes near someone they didn't know.)
58% of the time person B can name no person C with whom they had a CLOSE contact in the last week (or since 2 days before the first symptom).
Other than my spouse, I've had one close contact on one day in the last 8.5 months. (And, I didn't intend to have that one.)
You'd have to have a pretty sour view of humanity (at least, those people in SCC) to believe that more than half the people refuse to cooperate when lives of friends and coworkers may be at stake.
RE: Preprint: low temp, extreme relative humidity - Goose - 11-08-2020
(11-08-2020, 03:08 PM)M T Wrote: You'd have to have a pretty sour view of humanity (at least, those people in SCC) to believe that more than half the people refuse to cooperate when lives of friends and coworkers may be at stake.Well, that is what Dr. Morrow says is true in San Mateo County. Do you think Santa Clara County is that much better?
RE: Preprint: low temp, extreme relative humidity - M T - 11-08-2020
(11-05-2020, 10:44 PM)Snorlax94 Wrote: As for the speculation regarding fomites, I keep thinking back to that Korean call center study.I disagree. (and, by the way, you pulled "formidable" out of your air. I suggested no such thing.)
I think it was a 15 story building where they tested 1,145 contacts. The first case was on the 10th floor, but from then on, 97% of the confirmed cases were all on the 11th floor, and of those, almost all of them were in close range.
If fomites were such a formidable source of spread, I'd expect more of the infections to break out beyond the 11th floor, and to pass to co-workers on different floors and on the opposite side of the building.
I work among a set of people that work on the 2nd floor and basement of a building. I rarely touch anything not on my floors, except the door handles to go up/down the stairs and the entry/exit door. People that work on the first floor rarely touch the stair doors. Indeed, if I used the elevator, the only things I'd touch are the Up button on the first floor and the "2" button (which people on other floors would rarely touch).
I do believe this call center example is a good example of likely spread by aerosol. Indeed, the talking involved in a call center, could be why this would have more spread than monks in pews quietly praying. I wish the authors had also indicated where negative tests were -- we don't know that every position was occupied. The virus spread over 12 days (in that room) before the call center was shutdown. That could be at as much as 7 generations rather than one super-spreading event. (A friend's family was involved in 4 generations of infections in 6 days: A->B->C->D where C was not exposed to A nor was D exposed to A or B.) It could be droplet spread from person to person rather than an infectious aerosol cloud.
But just because drunk drivers cause a lot of accidents, doesn't mean that all accidents are due to drinking. If you reduce the amount of drunk driving, but still have too many accidents, maybe you need to look if there may be other causes rather than saying something like "One of the drivers must have been drinking even if we can't prove it; We have to work harder to stop drunk driving!"
RE: Preprint: low temp, extreme relative humidity - g1313 - 11-10-2020
Unfortunately my view of humanity has grown pretty sour. Really hard to estimate whether it is more than 50% or not, but I have personally seen healthcare professionals in santa clara county gather indoors in groups of 10+ for fun AND POST IT ON SOCIAL MEDIA.
(11-08-2020, 05:16 PM)Goose Wrote:(11-08-2020, 03:08 PM)M T Wrote: You'd have to have a pretty sour view of humanity (at least, those people in SCC) to believe that more than half the people refuse to cooperate when lives of friends and coworkers may be at stake.Well, that is what Dr. Morrow says is true in San Mateo County. Do you think Santa Clara County is that much better?