Mouth to Lungs: Dentists Explain Clinical Variability in Covid

Since the Covid outbreak first became known to the world over 18 months ago, great strides have been made in treatment and vaccination. However, there is relatively little understanding of why some people have a mild infection of the upper respiratory tract and others develop severe disease of the lungs requiring hospital treatment.

There is mounting evidence that gum disease may play a role in this “clinical variability” of Covid-19. A hypothesis published in the Journal of Oral Medicine and Dental Research (by two periodontists, a consultant radiologist and a research professor at the University of Birmingham) seeks to explain the pathway the disease may take from primary infection in  the upper respiratory tract, via saliva in the mouth, to the vascular system and severe infection in  the lungs.

Covid first takes hold in the upper respiratory tract binding to ACE2 receptors in the nasal cavity. One might assume therefore that the virus progresses down the airways to the lungs. However the lack of ACE2 receptors further down the airways suggests that this may not be the primary route. The authors of the article hypothesise an alternative: perhaps Covid present in saliva could pass through infected gums into the vascular system and reach the lungs that way?

Radiological evidence certainly seems to back this up: 

“Pulmonary radiological findings in COVID-19 do not align with a model of SARS-CoV-2 infection primarily causing disease of the airways of the lungs; the initial and dominant pathological features demonstrated radiologically are vascular in nature.”

The periodontal perspective shows the possible pathway that Covid-19 virus present in saliva could take.

“The periodontal pocket epithelium develops micro-ulcerations that facilitate the passage of microorganisms and viral particles to the underlying connective tissue and gingival capillary complex, reaching the systemic circulation.”

If proved true, this hypothesis could have a huge clinical significance. A drive towards improved gum health could have an impact on the numbers who are infected with Covid who go on to develop severe disease. 

Thanks to the NHS’s vaccination programme, the nation is already making inroads towards defeating this disease. What if good oral hygiene turns out to be another weapon in our fight against Covid? And one that we can all take up!