A study conducted by researchers at the University of Birmingham suggests the SARS-CoV-2 virus could travel to the lungs via the bloodstream from saliva, especially in individuals suffering from gum disease. Evidence was found that indicates it is the blood vessels rather than the airways which are initially affected in COVID-19 lung disease and high concentrations of the SARS-CoV-2 virus in saliva and periodontitis have been associated with an increased risk of death.
Reasons have been suggested as to why some individuals develop severe COVID-19 symptoms and others do not, but the reasons for the clinical variability of symptoms is not yet understood. The researchers propose a vascular route of transfer of the virus to the when the virus breaches the immune defenses in the mouth. Saliva is a reservoir of SARS-CoV-2 and could enter the bloodstream via the gingival sulcus or periodontal pocket and be transported to the small blood vessels in the lungs.
“The binding of the virus to the angiotensin-converting enzyme 2 receptor (ACE2), present on the endothelial surface of lung vessels, inactivates ACE2 and increases angiotensin-II levels, leading to pulmonary vasoconstriction and immunothrombosis,” explained the researchers. “This leads to vascular congestion, proximal vasodilatation, and subsequent lung parenchymal damage mediated by endothelial dysfunction.” Individuals with plaque accumulation and periodontal inflammation would intensify that pathway.
Maintaining good oral hygiene, including regular brushing, the use of certain mouthwashes, and interdental brushing could be a highly effective way of inactivating the virus in saliva and blocking this pathway. While these measures may not prevent individuals from contracting COVID-19, they could reduce the level of the virus and help to prevent severe infections.
Further, maintaining oral hygiene requires only simple, low-cost steps to be taken by individuals which would not only reduce the risk of developing severe COVID-19 symptoms but would also help to prevent gum disease.
“Gum disease makes the gums leakier, allowing microorganisms to enter into the blood. Simple measures – such as careful toothbrushing and interdental brushing to reduce plaque build-up, along with specific mouthwashes, or even saltwater rinsing to reduce gingival inflammation – could help decrease the virus’ concentration in saliva and help mitigate the development of lung disease and reduce the risk of deterioration to severe COVID-19,” said study co-author, Iain Chapple, Professor of Periodontology at the University of Birmingham.
Experts from the Mouth-Body Research Institute in Los Angeles and Cape Town and Salisbury District Hospital participated in the study, and it was observations from radiologist Dr Graham Lloyd-Jones of the Salisbury Radiology Group that led to a collaboration between researchers into the possible oral entry route of the virus into the bloodstream.
Further studies are now required to investigate the oral-vascular model of SARS-CoV-2 transfer to the lungs and the extent to which gum disease is linked to the most severe COVID-19 cases.
You can read more about the study in the paper – The COVID-19 Pathway: A Proposed Oral-Vascular-Pulmonary Route of SARS-CoV-2 Infection and the Importance of Oral Healthcare Measures – which was recently published in The Journal of Oral Medicine & Dental Research.