Blackmores Institute

<p></p><h3><strong> </strong></h3><h3><strong>Social distancing and immunity</strong></h3><p>The capacity for transmissible pathogens to reproduce with ease between people in close contact, prompted the implementation of non-pharmaceutical interventions such as social distancing, masks, lockdowns, and antimicrobial use.<sup>1,2</sup> While we were working to slow the spread of COVID-19, the transmission of other respiratory illnesses was stunted, with research finding reduced yearly influenza transmissions due to higher winter temperatures likely contributing to a more intense influenza season the following year.<sup>2</sup> The shift in exposure and immunity following social distancing measures has led to a resurgence of other epidemics and reduced herd immunity, as currently seen in Australian hospitals with unseasonably high numbers of respiratory syncytial virus in children.<sup>2</sup></p><p> </p><h3><strong>Social distancing and the microbiome</strong></h3><p>Social distancing impacts the diversity of the microbiome by minimising bacterial transmission opportunities between individuals, leading to reduced microbial diversity.<sup>3</sup> Physical contact, birthing technique, breastfeeding and surface contact through hands and mouth, support the inoculation of a diverse microbiome for babies and infants.<sup>3</sup> Future generations born during the pandemic may also have altered microbiomes as a result of higher caesarean delivery rates during COVID-19 proven to impact the newborn microbiota.<sup>4,5</sup></p><p></p><p> <em><strong>“The breaking of the contagion pathways reduces the sharing of microorganisms between people, thus favouring dysbiosis, which, in turn, may increase the poor prognosis of the disease.”</strong></em><sup>3</sup></p><p><sup> </sup></p><p> </p><img src="https://images.contentstack.io/v3/assets/blt948bd74310fc0ad0/blt0dc5c5cd7c512903/69f29b66f3d0cad73a98f607/immunity-article-graphic-august-17_8_22-1080x1080.jpg" alt="immunity-article-graphic-august-17_8_22-1080x1080.jpg" class="embedded-asset" /><p>Image: A model demonstrating COVID-19 prevention measures and their influence on microbial diversity throughout the lifetime. <sup>9</sup></p><h3><strong> </strong></h3><h3><strong>Antibacterial use and the microbiome</strong></h3><p>Furthermore, the increase in antibacterial products, handwash and hand sanitiser use may adversely impact the skin and gut microbiome. Beneficial skin and gastrointestinal bacteria are susceptible to destruction from hand sanitisers and alcohol, potentially leading to dysbiosis, gastrointestinal symptoms, inflammatory bowel diseases, obesity and chronic heart disease, and increasing the risk and severity of COVID-19.<sup>6</sup> Exposure to the antibacterial triclosan may lead to lifelong metabolic changes including childhood obesity and a reduction in microbial diversity in breastfed infants.<sup>7,8</sup></p><p></p><h3><strong> </strong></h3><h3><strong>Gut health</strong></h3><p>Dysbiosis is associated with immune dysregulation, increasing the prevalence of autoimmunity4 and chronic diseases such as asthma, diabetes and obesity.<sup>9</sup> COVID-19 itself has been attributed to changes in the gut microbiome with a reduction in <em>Lactobacillus</em> and <em>Bifidobacterium</em> species and short-chain fatty acid production, with beneficial bacteria inversely associated with viral load, COVID-19 severity, inflammation and upregulation of ACE2 receptors in the gut, lungs and oesophagus.<sup>4,9,10</sup> Of particular interest is the impact this has on the ability of the individual to mount an immune response to respiratory illnesses with alterations occurring to the oropharyngeal and gastrointestinal microbiomes.<sup>3</sup></p><p></p><h3><strong> </strong></h3><h3><strong>Respiratory health</strong></h3><p>The lung microbiota is a dynamic environment with the continuous bidirectional movement of air and mucus into the alveoli, with dysbiosis connected to lung pathologies.<sup>11</sup> Exposure to unhygienic environments and air microbes support stronger respiratory immune response development.<sup>11</sup> Dysbiosis in the respiratory microbiome reduces the protective symbiotic bacteria involved in the prevention of immune and autoimmune disease.<sup>3</sup></p><p></p><h3><strong> </strong></h3><h3><strong>Long term implications</strong></h3><p>The hygiene hypothesis connects many environmental, medical and dietary changes and increased hygiene with a reduction in microbiome diversity leading to a reduction in ancestral microbial heritage over time, which with generational loss may lead to microbial species extinction, known as the disappearing microbiota hypothesis.<sup>3,9</sup></p><p>As healthcare practitioners, it is important to support patients to promote a diverse microbiome and strong immune response through the consumption of a rich and diverse diet abundant in prebiotic and probiotic foods and supplements, and soluble and insoluble fibre from plant-based foods to support intestinal epithelial cell and microbiota health. Essential fatty acids, zinc, vitamin D and vitamin A are all supportive of both the immune system and the epithelial barrier and are integral to the immune response and the health of the microbiota.</p><p></p><h3><strong> </strong></h3><h3><strong>References</strong></h3><ol><li>Townsend A, Hawley D, Stephenson J, Williams K. Emerging infectious disease and the challenges of social distancing in human and non-human animals. Proceedings of the Royal Society B: Biological Sciences. 2020;287(1932):20201039. https://royalsocietypublishing.org/doi/full/10.1098/rspb.2020.1039</li></ol><p>2. Sanz-Muñoz I, Tamames-Gómez S, Castrodeza-Sanz J, Eiros-Bouza J, de Lejarazu-Leonardo R. Social Distancing, Lockdown and the Wide Use of Mask; A Magic Solution or a Double-Edged Sword for Respiratory Viruses Epidemiology?. Vaccines. 2021;9(6):595. <a href="https://www.mdpi.com/2076-393X/9/6/595" target="_blank" style="">https://www.mdpi.com/2076-393X/9/6/595</a></p><p>3. Domingues C, Rebelo J, Dionisio F, Botelho A, Nogueira T. The Social Distancing Imposed To Contain COVID-19 Can Affect Our Microbiome: a Double-Edged Sword in Human Health. Sphere. 2020;5(5). <a href="https://journals.asm.org/doi/full/10.1128/mSphere.00716-20" target="_blank" style="">https://journals.asm.org/doi/full/10.1128/mSphere.00716-20</a></p><p>4. Littlejohn P, Finlay B. When a pandemic and an epidemic collide: COVID-19, gut microbiota, and the double burden of malnutrition. BMC Medicine. 2021;19(1). <a href="https://doi.org/10.1186/s12916-021-01910-z" target="_blank" style="">https://doi.org/10.1186/s12916-021-01910-z</a> </p><p>5. Dowd J, Renson A. “Under the Skin” and into the Gut: Social Epidemiology of the Microbiome. Current Epidemiology Reports. 2018;5(4):432-441. <a href="https://doi.org/10.1007/s40471-018-0167-7" target="_blank" style="">https://doi.org/10.1007/s40471-018-0167-7</a> </p><p>6. Chandanapalli Sai Himabindu C, Bitra Tanish B, Damodara Padma priya D, Nimmala Prema Kumari N, Shaik Nayab S. Hand sanitizers: is over usage harmful ?. World Journal of Current Medical and Pharmaceutical Research. 2020;:296-300. <a href="https://www.researchgate.net/publication/344734032_Hand_sanitizers_is_over_usage_harmful" target="_blank" style="">https://www.researchgate.net/publication/344734032_Hand_sanitizers_is_over_usage_harmful</a></p><p>7. Ejtahed H, Hasani-Ranjbar S, Siadat S, Larijani B. The most important challenges ahead of microbiome pattern in the post era of the COVID-19 pandemic. Journal of Diabetes &amp; Metabolic Disorders. 2020;19(2):2031-2033. <a href="https://doi.org/10.1007/s40200-020-00579-0" target="_blank" style="">https://doi.org/10.1007/s40200-020-00579-0</a> </p><p>8. Sanidad K, Xiao H, Zhang G. Triclosan, a common antimicrobial ingredient, on gut microbiota and gut health. Gut Microbes. 2018;10(3):434-437. <a href="https://doi.org/10.1080/19490976.2018.1546521" target="_blank" style="">https://doi.org/10.1080/19490976.2018.1546521</a></p><p>9. Finlay B, Amato K, Azad M, Blaser M, Bosch T, Chu H et al. The hygiene hypothesis, the COVID pandemic, and consequences for the human microbiome. Proceedings of the National Academy of Sciences. 2021;118(6). <a href="https://www.pnas.org/doi/epdf/10.1073/pnas.2010217118" target="_blank" style="">https://www.pnas.org/doi/epdf/10.1073/pnas.2010217118</a> </p><p>10. Janda L, Mihalčin M, Šťastná M. Is a healthy microbiome responsible for lower mortality in COVID-19?. Biologia. 2020;76(2):819-829. <a href="https://doi.org/10.2478/s11756-020-00614-8" target="_blank" style="">https://doi.org/10.2478/s11756-020-00614-8</a> </p><p>11. Khatiwada S, Subedi A. Lung microbiome and coronavirus disease 2019 (COVID-19): Possible link and implications. Human Microbiome Journal. 2020 Aug;17:100073. <a href="https://doi.org/10.1016/j.humic.2020.100073" target="_blank" style="">https://doi.org/10.1016/j.humic.2020.100073</a> </p>

<p>Australians are learning to live with the multitude of circulating respiratory viruses following the lifting of social distancing measures and the subsequent increase in workplace, school, and childcare absences. Our article looks at the potential ramifications to immune health with the increased hygiene protocols and social distancing implemented during the pandemic, focusing on the microbiome and immunity.</p>

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