The Oral-Systemic Link: A Review about the strong Correlation between Diabetes mellitus, Periodontits and COVID-19 Outcome

The SARS-CoV-2 virus leads to symptoms ranging from mild flu symptoms to severe COVID-19 pneumonia requiring mechanical ventilation and even death. According to epidemiological observations, diabetes mellitus is a major risk factor for severe outcome, next to older age, s, hypertension, and other serious chronic illnesses. Recent studies have determined that the oral cavity mucosa is the main entry portal for the SARS-CoV-2 virus into the body. The viruses accumulate in the mouth at locations where the main viral receptor is highly expressed. The oral pathway of the virus into the body and the contributing factors are described in this review. The immune system of people with diabetes is generally impaired. Diabetes induces chronic systemic inflammation, which regularly manifests as periodontitis in the oral cavity. Furthermore, frequent hyperglycemia leads to additional weakening of the mucosal immune barrier. These findings provide plausible explanations for the more frequent severe courses of respiratory viral infections in diabetes patients. An oral examination helps to identify patients at elevated risk. Activated matrix metalloproteinase-8 (aMMP-8) is an established biomarker for measuring the degree of oral inflammation and is an indicator of the destruction of collagen and bone structures in the mouth. aMMP-8 point-of-care tests are readily available. We propose that the current recommendations for the prevention of SARS-CoV-2-associated severe COVID-19 disease should be extended to consider the aspects of measuring and sanitizing oral health, as well as to include preventive regular daily disinfection of the mouth and the pharynx.