New Info on COVID, the Immune System and the Microbiome

With every passing weeks, it seems like more connections are being  made between the bacterial microbiome and severe COVID-19 infection.  A new paper was pre-published (not yet peer reviewed) late last week looking in  more depth at the microbiota in COVID and what’s happening in the immune system.[i]  By late July, it seemed that the medical establishment was generally accepting that severe COVID is in actuality, an acute inflammatory disorder:  “Although over 90% of infected individuals are asymptomatic or manifest noncritical symptoms and will recover from the infection, those individuals presenting with critical symptoms are in urgent need of effective treatment options….A critical literature review suggests that the severity of SARS-CoV-2 infection is associated with dysregulation of inflammatory immune responses…”[ii]

My regular readers know that body fat is actually an organ, and  excretes heaps of proinflammatory cytokines.  (Check out this post, as just one example.) The fact that those who are overweight are experiencing more severe COVID symptoms was first hinted at months ago, but not confirmed until recently.  This from last week:  “People who are overweight, even if only modestly, are at greater risk of COVID-19 hospitalization…”[iii]  A BMI of 25-30 is considered overweight; over 30 is considered obese.  In this study, the researchers found that those with a BMI over 25 had a 40% higher risk of hospitalization, and those with a BMI over 30 had a 70% higher risk.  The heavier the person, the greater the risk.

And these scientists didn’t just find this correlation with BMI, by the way.  They also looked at wasit-to-hip ratios and found the same.  Why? Those who are overweight tend to already be in a constant state of low-grade inflammation:  their immune systems are primed to overreact.  And, as one of the authors of this paper points out, “Since over two-thirds of Westernized society are overweight or obese, this potentially presents a major risk factor for severe COVID-19 infection and may have implications for policy.”[iv]  This research, as well as previous, shows that low levels of HDL (good cholesterol), abnormal glucose metabolism (pre-diabetes, metabolic syndrome, diabetes), increase the risk of hospitalization.

Remember too:  those who are overweight also tend to have altered gut bacteria.  So, back to today’s research:  it appears that COVID infects intestinal tissue, and both viral RNA and infectious viral particles have been found in feces for over 30 days.  The researchers in this yet-to-be published study looked at a particular proinflammatory cytokine (IL-18) which is excreted by intestinal cells and found it to be higher than normal in COVID patients.  They also looked at IgA, which is intestinal antibodies:  they confirmed previous findings by other researchers.  COVID-19 severity is correlated to IgA levels.[v]

These scientists looked at 62  COVID patients, and compared them to 33 with ordinary flu and 40 healthy controls.  COVID patients had less diverse microbiota  than the other two cohorts, and they also had altered biomes:  “…Streptococcus, Clostridium, Lactobacillus, and Bifidobacterium were over-represented, and the genera Bacteroidetes, Roseburia, Faecalibacterium, Coprococcus, and Parabacteroides were fewer.”  The conclude that, “The increased abundance of Streptococcus in COVID-19 patients was indicative of the risk of infection by opportunistic pathogenic bacteria in this group.”

The upshot is that it is likely that dysbiosis of the gut bacteria contributes to disease severity.  Considering that altered gut microbiota is also associated with inflammation and obesity, as well as glucose metabolism issues, well…this all makes perfect sense.

I’ll continue to monitor all COVID-biome research and report to you as more information becomes available.


[i] Tao, W, et. al. Analysis of the intestinal microbiota in COVID-19 patients and its correlation with the inflammatory factor IL-18 and SARS-CoV-2 specific IgA.  Preprint medRxiv.  August 2020. Not yet peer reviewed.

[ii] Manjili RH, Zarei M, Habibi M, Manjili MH. COVID-19 as an Acute Inflammatory Disease. J Immunol. 2020;205(1):12-19. doi:10.4049/jimmunol.2000413




2 Comments on “New Info on COVID, the Immune System and the Microbiome

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