Hypothesis: SARS-CoV-2 amplifies pre-existing dysbiosis induced mucosal
inflammation and this can cause a severe systemic inflammatory disease. The
microbial flora perturbation can persist long after the virus has been eliminated
leading to a wide range of long Covid symptoms.
Evidence: Dysbiosis induced mucosal inflammation increases with age and
is strongly associated with the metabolic syndrome (obesity, type 2 diabetes
mellitus, ischaemic heart disease, hypertension, and depression). These are
risk factors for the conversion of mild to severe Covid-19. Certain common
strains of Staphylococcus aureus, which is commonly carried in pharyngeal
mucosa, can trigger a cytokine cascade as seen in severe Covid-19. Blood
group A and vitamin D deficiency, which are risk factors for hospitalisation in
Covid-19 are also associated with increased S. aureus pharyngeal carriage
rates. Multi-inflammatory syndrome in children is a post Covid condition which
resembles toxic shock syndrome and Kawasaki disease (the former is known
to be caused by staphylococcal pyrogenic toxins). A number of studies have
shown dysbiosis of the oral mucosa and rectal mucosa in patients who progress
to severe Covid-19. The wide range of pathology seen during and following
SARS-CoV-2 infection is more in keeping with dysbiosis induced inflammation
(multiple pathogenic bacteria at multiple sites) than with an otherwise simple
viral induced respiratory tract infection.
Implication: Optimization of the microbial flora, prior to encountering the
virus, could have reduced the severity of the pandemic. The consumption
of fermented foods, especially yoghurt, holds the most promise for reducing
dysbiosis induced mucosal inflammation and preventing a wide range of
complications. Reduced mucosal inflammation brings not only health but also
happiness in which oxytocin has a key role.