[FRIAM] preprint aerosol covid

Thu Jan 13 06:45:28 EST 2022

Dave, quick comment (probably superseded by things others have said and I haven’t read through yet).

Herd immunity thresholds depend on the transmission number, which depends on both molecular and cultural factors.

At the time the early numbers like 70% were put out, we had COVID-19 1.0, and we were saying “thank God it is so much less transmissible than measles, because it has so much higher case fatality”.  But there has since been an expansion by something like a factor of 6 in the molecular dimension of transmissibility, and Omicron is about as transmissible as measles, in one of the posts somebody here sent around.  So protections that put the in-situ R_0 below 1 with the original wild type are hopelessly inadequate with Omicron.  We will have to run much faster than that if we want to get anywhere.

Whatever herd immunity threshold there is for Omicron would probably have to be compared with measles, for which we seem to have been trying for near-universal childhood vaccination to stay close to eradication.  But I don’t have a good source for numbers and a structural description of the kind of barrier one wants, if such is even definable for an adult-onset disease.

Eric

> On Jan 12, 2022, at 5:01 PM, Prof David West <profwest at fastmail.fm> wrote:
> 
> "I wonder how many of us are back in lockdown and aren’t telling each other?"
> 
> CDC head on one of the Sunday news shows; responding to some comments made by earlier by Sotomayer about Covid (convoluted intro because I forgot name and which show), stated that 78% of those dying or having severe problems with COVID had "four or more comorbidity factors." Long ago, Italy reported that 90% of those who died from Covid had comorbidity factors.
> 
> It those kind of statistics that primarily affect any decision I might make about lock down. Masks and vaccination are being done, not for me, but because the latter is still the mandate here and the former because I desire to travel to Europe again.
> 
> Headline today said Omicron has run out of hosts. Multiple headlines/stories setting expectation for massive plunge in cases over next week, 10 days.
> 
> Where can I find accurate estimate of number of people in US that have been vaccinated or recovered from the disease and have antibodies.  A year ago, it was said that when this number hit between 70-80 percent we should have de facto herd immunity, but no one seems to talk about this anymore.
> 
> davew
> 
> 
> On Wed, Jan 12, 2022, at 9:20 AM, thompnickson2 at gmail.com <mailto:thompnickson2 at gmail.com> wrote:
>> I wonder how many of us are back in lockdown and aren’t telling each other? 
>>  
>> Or, how many of us think we should be in lock down, but aren’t.   This little voice keeps saying to me (you know, my “inner” voice) “Nick.  This omicron thing is going to be terrifying for the next six weeks and then be gone.  The hospitals are going to be jammed.  Not a time to risk any kind of medical emergency, let alone COVID.  Stay home.  Avoid icy pavements.  No sneaking off for coffee.” 
>>  
>> If Marcus is worrying about transmission in parks, maybe that time  has come.
>>  
>> Nick Thompson
>> ThompNickSon2 at gmail.com <mailto:ThompNickSon2 at gmail.com>
>> https://wordpress.clarku.edu/nthompson/ <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2fwordpress.clarku.edu%2fnthompson%2f&c=E,1,7VXPPIjuUdnq2wi9RbOt1Oao2IAUngldCVej7ovK8QIAFourS2HLIi8WU6WGWtTv7z6Or09G-VOWeLOQ0h8CUqfC1DQg3TXPXbJwLopU77miouf9RCvt&typo=1>
>>  
>> From: Friam <friam-bounces at redfish.com <mailto:friam-bounces at redfish.com>> On Behalf Of Marcus Daniels
>> Sent: Wednesday, January 12, 2022 11:03 AM
>> To: friam at redfish.com <mailto:friam at redfish.com>
>> Subject: Re: [FRIAM] preprint aerosol covid
>> 
>>  
>> Yesterday I was feeling nervous about being in the park.  It was super still but also high humidity.  Are people wearing masks outside?  This makes me think I should again?
>>  
>> Marcus
>> 
>> From: Friam <friam-bounces at redfish.com <mailto:friam-bounces at redfish.com>> on behalf of glen <gepropella at gmail.com <mailto:gepropella at gmail.com>>
>> Sent: Wednesday, January 12, 2022 9:59 AM
>> To: friam at redfish.com <mailto:friam at redfish.com> <friam at redfish.com <mailto:friam at redfish.com>>
>> Subject: Re: [FRIAM] preprint aerosol covid
>>  
>> Yeah, I enjoyed the closed rooms at lockheed. But only the 60Hz ones. The 400Hz rooms were horrible. If the results check out, it spells trouble for me, though, hanging out in breweries ... which usually have higher than normal relative humidity. Stupid virus.
>> 
>> On 1/12/22 08:56, Marcus Daniels wrote:
>> > We have enough air purifiers to filter the air in the house six times an hour.  It reminds me of the days when I had bitcoin miners running.
>> > The noise is like being in an airplane all the time.   I rather like fan noise though.   I could sleep in a machine room.
>> > 
>> > Marcus
>> > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>> > *From:* Friam <friam-bounces at redfish.com <mailto:friam-bounces at redfish.com>> on behalf of glen <gepropella at gmail.com <mailto:gepropella at gmail.com>>
>> > *Sent:* Wednesday, January 12, 2022 9:25 AM
>> > *To:* friam at redfish.com <mailto:friam at redfish.com> <friam at redfish.com <mailto:friam at redfish.com>>
>> > *Subject:* [FRIAM] preprint aerosol covid
>> > The Dynamics of SARS-CoV-2 Infectivity with Changes in Aerosol Microenvironment
>> > https://www.medrxiv.org/content/10.1101/2022.01.08.22268944v1 <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2fwww.medrxiv.org%2fcontent%2f10.1101%2f2022.01.08.22268944v1&c=E,1,xEE9olFfkZlJjN9Ih-m-bKCBZTm6nYvVFSXMQCZ7BAH0IVWWDB7qV_KsgjfzSbNVnc27Ggr9BjqvPzlbd5w1B2rLxma29F5usRLYlLlzAKs3Mie6hSQ,&typo=1><https://www.medrxiv.org/content/10.1101/2022.01.08.22268944v1 <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2fwww.medrxiv.org%2fcontent%2f10.1101%2f2022.01.08.22268944v1&c=E,1,WeMbLpczs0RnehM7qqNLVWoV0iBl8PfZZm6GDl2xr64nsc-E2Z7VDPgmppw21_aXvt_tgJzZeG9gNBNkS_YzT2wGx9Tbik_DqM57etIaEJajUMSEv7fU4rc,&typo=1>>
>> >> Understanding the factors that influence the airborne survival of viruses such as SARS-CoV-2 in aerosols is important for identifying routes of transmission and the value of various mitigation strategies for preventing transmission. We present measurements  of the stability of SARS-CoV-2 in aerosol droplets (∼5-10µm equilibrated radius) over timescales spanning from 5 seconds to 20 minutes using a novel instrument to probe survival in a small population of droplets (typically 5-10) containing ∼1 virus/droplet. Measurements of airborne infectivity change are coupled with a detailed physicochemical analysis of the airborne droplets containing the virus. A decrease in infectivity to ∼10 % of the starting value was observable for SARS-CoV-2 over 20 minutes, with a large proportion of the loss occurring within the first 5 minutes after aerosolisation. The initial rate of infectivity loss was found to correlate with physical transformation of the equilibrating droplet; salts within the droplets crystallise at RHs below 50% leading to a near instant loss of infectivity in 50–60% of the virus. However, at 90% RH the droplet remains homogenous and aqueous, and the viral stability is sustained for the first 2 minutes, beyond which it 
>> > decays to only 10% remaining infectious after 10 minutes. The loss of infectivity at high RH is consistent with an elevation in the pH of the droplets, caused by volatilisation of CO2 from bicarbonate buffer within the droplet. Three different variants of SARS-CoV-2 were compared and found to have a similar degree of airborne stability at both high and low RH.
>> 
>> -- 
>> glen
>> Theorem 3. There exists a double master function.
>> 
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