New Study's Data Conflicts with what We

Know about Asymptomatic Covid-19 Patients

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June 18th - 

Recent research data conflicts with what we know about asymptomatic patients.

 

In the study, 37 asymptomatic cases were tracked, defined as individuals with a positive nucleic acid test result but without any relevant clinical symptoms in the preceding 14 d and during hospitalization. 
 

These were compared to a total of 178 peer patients who were confirmed to have SARS-CoV-2 infections in the Wanzhou District of China, as pulled from the same quarantine testing pool. 

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The key results were: 

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  • Of the 178 laboratory-confirmed patients, 37 who never developed any symptoms throughout the disease course were included in this study, this equates to 20.8% of patients having asymptomatic infections.

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  • The proportion of asymptomatic infections might be even higher as some cases might be missed by RT–PCR testing. The study successfully identified seven patients who had active SARS-CoV-2 infection from 148 cases that had negative RT–PCR results and no symptoms by using an antibody test

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  • A possible reversal of previously documented data, among asymptomatic patients it was found the median duration of viral shedding was 19 days, compared to 14 days for those who had mild symptoms.

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  • Asymptomatic individuals exhibited lower levels of 18 different pro and anti-inflammatory cytokines. These data suggest that asymptomatic individuals had a weaker immune response to SARS-CoV-2 infection.

  

https://www.nature.com/articles/s41591-020-0965-6

Surface Transmission Not a Significant Proportion of Covid-19 Cases

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In April, the New England Journal of Medicine published definitive data regarding the duration in which corona-virus particles remain viable in the air and on common surfaces. To quickly recap the notable findings: 

  • The initial number of viable virus particles in the air halves after about 1 hour. 

  • Viral particles in the air can remain infectious for several hours. 

  • After 4 hours, essentially all viable virus particles stop existing on copper.

  • After 24 hours, essentially all viable virus particles stop existing on cardboard. 

  • After 72 hours, essentially all viable virus particles stop existing on steel and plastic. 

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Read the full study here: https://www.nejm.org/doi/10.1056/NEJMc2004973

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However, important recent guideline changes from the CDC suggest that viral transmission from contaminated surfaces does not make up a significant proportion of Covid-19 cases and that “the virus does not spread easily in other ways.” It's important to note that physical transmission can still happen, but that its not anywhere near as important as keeping a distance from others, and moving away from enclosed spaces with multiple people. 

 

The succinct CDC guidelines are available here: 

https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-covid-spreads.html  

JAMA Transmission Data Paints a Clearer Picture About Covid-19 Risk  

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May 27th - 

New research data suggests that asymptomatic patients are:

  • More likely to be women.

  • More likely to be younger. 

  • Shed SARS-CoV-2 viral particles for about 8 days, compared with 19 days for symptomatic patients.

  • Less overall consumption of CD4+T lymphocyte in asymptomatic infections ​(which implies that asymptomatic infection is accompanied by less adverse effects upon the immune system then symptomatic infection).

 

Do note, reduced duration of viral shedding is not the same as viral load ( the amount of viral particles expelled in respiratory droplets) – these two separate factors are a separate variable this study did not test for. 

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Recent circulating information suggest it is likely the number of asymptomatic, ‘silent’ COVID-19 infections are clearly more prevalent than initial estimates. 

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Some asymptomatic patients may act as COVID-19 ‘super spreaders’, but this study demonstrates that is probable that they will not be contagious for as long as comparable symptomatic patients.

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https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2766237