Oral Cavity: A Nursery for Coronavirus Dr. John A Lopes Ph.D.
COVID-19 is primarily an infection of the lungs, upper airways, and nasal cavity. Coronavirus 2 (SARS‑CoV‑2), the causative agent, has multiple attachment ligands (molecules) that can bind to and infect cells in oral cavity, eyes, the digestive system, blood vessels, kidneys, and potentially other mucosal surfaces. Dr. Huang and colleagues have reported that coronavirus 2 (SARS‑CoV‑2) that produces COVID-19 infection can actively infect cells that line the mouth and salivary glands (Nat. Med. 2021 Mar 25.). Almost half of COVID-19 cases include oral symptoms, such as loss of taste, dry mouth, and oral ulcer. Such symptoms could also be due to infection of the olfactory tissues in the nose.
Dental Researchers Dr. Blake Warner (NIH), Dr. Kevin Byrd Univ. of North Carolina and colleagues found that a small portion of salivary gland and gingival (gum) cells around our teeth, simultaneously expressed the genes for encoding proteins: ACE2 receptor protein and TMPRSS2 enzyme protein required for the virus to bind and enter the cells, pointing to potential sites for attachment and growth of Coronavirus 2 (SARS‑CoV‑2).
Besides the large mucosal surface in the oral cavity, salivary glands present additional potential surfaces for binding and growth of the virus. In addition to the hundreds of smaller salivary glands, there are three large pairs of salivary glands including, a) parotid glands present in front of and just below each ear, b) submandibular glands below the jaw and, c) sublingual glands under the tongue. Although saliva keeps the mouth clean and healthy because it contains antibodies that kill germs, it can be a source of coronavirus 2 (SARS‑COV‑2) transmission.
The scientists detected signs of SARS-CoV-2 in just over half of the salivary gland tissue samples that it examined from people with COVID-19 including one person who had died from COVID-19 and another with acute illness. The researchers also found evidence that the coronavirus was actively replicating to make more copies of itself. In people with mild or asymptomatic COVID-19, oral cells that shed into the saliva bathing the mouth were found to contain RNA for SARS-CoV-2, as well as the proteins that it uses to enter human cells.
The researchers also found that saliva from asymptomatic COVID-19 people when added to healthy cells grown in a lab dish infected the healthy cells. These findings raise the unfortunate possibility that even people with asymptomatic COVID-19 might unknowingly transmit SARS-CoV-2 to other people through their saliva. Thus, any activities that involve direct or indirect contact with saliva droplets like speaking or breathing unmasked, singing in public can easily spread the virus infection.
There is a silver lining to this grim situation with the highly infective SARS-CoV-2 virus. Microcide Dentoral broad spectrum antimicrobial alcohol free mouthwash has been tested against SARS-CoV-2 and found to be highly effective by killing 99.999% of the virus in suspension test at prestigious national testing facility.
Huang, N., Pérez, P., Kato, T. et al. SARS-CoV-2 infection of the oral cavity and saliva. Nat Med (2021). https://doi.org/10.1038/s41591-021-01296-8.