I had a discussion with my neighbor about whether asymptomatic or presymptomatic COVID transmission has been proven.
I did some research.
This is what I found
Per our discussion, I reviewed a number of research articles on the topic of asymptomatic and presymptomatic transmission — listed below. These articles all complained about lack of data, from which to draw conclusions. Moreover, it is hard to say who has symptoms, since many people lie about it https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2797071
The gold standard of medical testing is the controlled double blind test. No such test appears. What appears is small scale contact tracing, where some anecdotal asymptomatic and presymptomatic transmission was confirmed. The articles generally concluded that such transmission is possible, with presymptomatic transmission being more likely than asymptomatic transmission.
They do conclude that there is more transmission from people with symptoms — but, then again, no controlled double blind testing.
What they were able to document was viral load with respect to symptom onset. In this respect, I note https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7310638/ and in particular figure 2 of this article, an image of which is enclosed. This shows viral load relative to symptom onset. The colors on this graph represent statistics vocabulary that I have not researched. However, there is viral load above the level of transmissibility prior to symptom onset in 3 out of 4 of these curves.
These curves do, as you indicated, show viral load increasing after symptom onset, contrary to what is commonly stated.
Otoh, I’m not sure, from a practical viewpoint, what the difference might be between contracting the disease from people who have no symptoms v contracting the disease from people who are lying about having no symptoms, or people who mistakenly believe they have allergy or GERD symptoms.
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These are articles that I looked at, not date order, but rather in google order — where later studies with more data apparently tend to appear after earlier studies with less data.
https://www.pnas.org/doi/10.1073/pnas.2019716118
https://pubmed.ncbi.nlm.nih.gov/34217301/
https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-022-07440-0
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7310638/ (review of articles)
https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003987
https://www.frontiersin.org/articles/10.3389/fcimb.2022.836409/full
https://www.advisory.com/daily-briefing/2022/06/02/covid-transmission
https://www.cidrap.umn.edu/news-perspective/2022/05/news-scan-may-27-2022
https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-022-07440-0
Curious -- research showing symptoms peaking after symptom onset rather than before, contrary to popular sayings https://t.co/rLxiDUR7e5 pic.twitter.com/RqxTH3vU2k
— AnneBarschall (@AnneBarschall) November 7, 2022
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