COVID: airborne transmssion, again...

 Another article very strongly suggested airborne transmission of SARS-CoV-2 virus (see covid airborne transmission jamaintmed2020, or doi:10.1001/jamainternmed.2020.5225).  I am bringing this up, again, since Trump just praised a "spectacular" doctor who dismissed the use of face masks.....

Details:

--128 people riding one of 2 buses to attend a worship event in Eastern China on January 19th. there were no prior cases of Covid-19 in this city (Ningbo city), and none were reported until January 20th, when there was a total of 69 cases reported of 8 million people living in the city

--12% men, mean age 59

--bus ride was 100-minute round-trip and a 150-minute worship session

--there was a 15-30 minute luncheon (10 attendees sitting at roundtable in spacious room), with people randomized to the tables

--no toilets on the buses, no people changed seats on the way back

--weather was sunny with gentle breeze

--bus 1: 60 people 

--bus 2: 68 people

    --one patient on bus 2 was initially asymptomatic with SARS-CoV-2

        --this index case was in his 60s and the only person traveling who was exposed to residents from Wuhan

        --this person was asymptomatic on the bus trip but developed symptoms of cough, chills and myalgias after returning home that evening; and he and several family members subsequently had PCR-confirmed Covid-19

    --zones on the bus were divided into high- vs low-risk, depending on distance from the infected person (cutpoint: 2 meters or 3 rows of seats)

--in both buses, they had central air conditioners set for indoor recirculation mode

--throat swabs (oropharynx and nasopharynx) were collected for all individuals involved in the outbreak, as well as their close contacts identified through subsequent contact tracing

Results:

--24 of the 68 on bus 2 (35%) were diagnosed with Covid-19 after the event; none on bus 1 were

    --those on bus 2 were 42-times more likely to develop Covid-19 than those on bus 1

    --2 were asymptomatic, 3 mild symptoms, 17 moderate symptoms

 --individuals in closer proximity to the index case in bus 2 (high-risk) had a moderate but nonsignificant higher rate of developing Covid-19 than those in the low-risk zone

--none of those on bus 2 who were sitting close to the windows (where the air vents were) or to the door developed infection

--of the other, non-bused participants (172 people) at the event: relative risk 1.6 (0.8-3.2)

    --7 developed covid-19 (4%), all describing close contact with the index case

    --those in bus 2 had a 34% higher risk of Covid-19, and were 11.4 times more likely to get Covid-19 than those not on either bus

--review of timetable: most others developed Covid-19 3-6 days after exposure to index patient, and there continued to be primary cases up to 4 weeks later, with several subsequent transmissions for up to 3 generations until 5 weeks later 

Commentary:

--aerosol transmission has been suspected in several prior studies: eg see https://commonwealthmagazine.org/environment/coronavirus-risks-know-them-avoid-them/ , or http://gmodestmedblogs.blogspot.com/2020/06/covid-readers-comments-retracted.html

--and, of course, this aerosol transmission reinforces the importance of personal protection: esp social distancing and masks

--a few notable aspects of this study:

    --this was basically a controlled trial, with apparently one bus having a patient with Covid-19 and the other no known infections

    --transmission occurred when the patient was asymptomatic, though evidently still a "super-spreader"

    --this patient was likely the index case since he developed symptoms later that night

        --the timing of transmission is consistent with other studies: very high viral loads in the 2-3 days prior to becoming symptomatic

    --the recirculating air likely spread aerosolized virus throughout the bus, as evidenced by the lack of clear association between the index patient and proximity of those getting secondary infections (2 patients were separated from the index patient by >5 meters)

        --this conclusion about recirculating air was reinforced by the significantly decreased transmission rate in those with close contact when off the bus

        --and the widespread viral transmission reinforces that spread was from aerosolized air and not by direct droplet contact with the virus

--very unfortunately, one of our major publicists on all things Covid (Trump) has very recently again promoted against mask wearing (see https://www.theguardian.com/us-news/2020/jul/28/trump-covid-19-briefing-hydroxychloroquine-video ), citing a "spectacular" doctor's wisdom.

    --among the other spectacular insights proclaimed by this "spectacular" doctor Stella Immanual, who, per Trump, "has had tremendous success with hundreds of different patients" with hydroxychloroquine, noting that since there is a cure for Covid-19, no need for masks:

        --doctors make medicine using DNA from aliens

        --doctors are trying to create a vaccine to make one immune from becoming religious

        --gynecologic problems like cysts and endometriosis are in fact caused by people having sex in their dreams with demons and witches

        --and, no doubt, many more spectacular insights

so, no surprises that there can be aerosolized transmission of SARS-CoV-2.  the reasons i bring this up now:

--we are submersed in an anti-science atmosphere, where Trump is lauding complete fringy weirdos

--his validation of them may actually influence many voters

--and, this might lead to decreased mask use, and its likely attendant increases in Covid-19 cases and deaths (and, it does turn out that, despite Trump's broadcasting of right-wing conspiratorialists' numbers, the death count is actually more than 9000!!!, by a factor of at least 20: see https://www.cnbc.com/2020/09/01/fauci-debunks-theories-of-low-cdc-coronavirus-death-toll-there-are-180000-plus-deaths-in-us.html )

    --of note, there is currently a resurgence of cases in Korea, despite their aggressive initial policies (see https://www.nytimes.com/2020/09/02/world/asia/south-korea-covid-19.html ), reinforcing the importance of NOT relaxing our current approach, though that is still less aggressive and consistent than it should be

--and, also these shenanigans decrease respect for and acceptance of the actions of the CDC and FDA by many

above and beyond that, this study:

--reinforces viral transmissibility from asymptomatic individuals. this conclusion is well-documented, though is also being undercut conceptually by Trump and CDC, which recently changed recommendations by diminishing the need to test asymptomatic people, even those in close contact (<6-feet) for at least 15 minutes. see https://www.cdc.gov/coronavirus/2019-ncov/hcp/testing-overview.html

    --and, of note, this asymptomatic person was a super-spreader

--adds further support to the pretty-well documented spread of the virus through aerosol

--reinforces that recirculated air is not the best ventilation system to use in this Covid-19 era

--reinforces masks and social distancing as preventative measures

--and reinforces that it is generally better to congregate in the open air than in closed spaces (though distancing studies suggest that the 6-foot distance may be suboptimal: see http://gmodestmedblogs.blogspot.com/2020/08/covid-transmission-and-distancing.html)

geoff

 

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