How COVID-19 Complications Can Start in the Mouth

COVID-19 has been an unfortunate occurrence that has been with us almost two years. Since one of the only things that was known about the novel coronavirus at first was that it spreads rapidly, many measures have been taken to help reduce the spread of COVID-19. Many of these measures are still continuing since there is still much that is unknown about the virus. One of the most accepted hypotheses is that the virus spreads through respiratory droplets that are inhaled into the lungs. However, a recent study has begun to question this hypothesis by proposing another theory. 

In the article, titled The COVID-19 Pathway: A Proposed Oral-Vascular-Pulmonary Route of SARS-CoV-2 Infection and the Importance of Oral Healthcare Measures, researchers propose that the SARS-CoV-2 virus does not reach the lungs through inhalation, but through the bloodstream. They partially attribute this to the fact that COVID lung infections are not consistent with inhaled pathogens because they are localized to the base of the lungs, while lung infections caused by inhaled pathogens are distributed all over the lungs. The article also presents various other arguments as to why researchers do not believe that the virus reaches the lungs through inhalation. 


Instead of being inhaled, the researchers behind the article believe that the virus starts in the mouth, passes into the bloodstream, and is then circulated to the blood vessels at the base of the lungs. Along with this new theory on how the virus reaches the lungs, researchers have also noticed a correlation between severe COVID-19 infections and periodontitis, which they believe strengthens their claim. 

Researchers have found elements that allow for COVID infection in the gingival tissue, minor salivary glands, and tongue. Because of this, they state that the mouth can become a potential reservoir for the virus to collect and replicate. However, the researchers also note that this can be especially problematic for individuals with periodontitis. For starters, this is because people with periodontitis have higher levels of gingival crevicular fluid (GCF), which is produced by the body in response to inflammation. Unfortunately, the SARS-CoV-2 virus has been identified in the GCF of 64% of people with COVID. 

Not only do people with periodontitis have higher levels of GCF which may or may not contain excess amounts of the virus, but they also have periodontal pockets. Periodontal pockets form when the gums pull away from the teeth, causing small gaps to form between the teeth and gums. These pockets tend to trap plaque and bacteria, which makes them an ideal environment for bacteria to reproduce. Unfortunately, when too much bacteria accumulates in the pockets, this can overwhelm the mouth’s immune defenses and allow the bacteria to enter the bloodstream. When oral bacteria enter the bloodstream, they can cause pregnancy complications, endocarditis, and respiratory infections. 

Since the SARS-CoV-2 virus has been identified in GCF, researchers now believe that the virus can accumulate in the periodontal pockets the same way as bacteria. This also means that the virus can continue to replicate until it eventually overwhelms the mouth’s immune defenses and passes into the bloodstream. Once in the bloodstream, the virus can travel to different parts of the body just as the bacteria can. However, circulation takes the virus from the mouth down into the chest and into the heart where it is then pumped into the pulmonary blood vessels of the lungs. 

how COVID reaches the lungs through the bloodstream
Image Source: https://www.genesispub.org/j-oral-med-and-dent-res/the-covid-19-pathway-a-proposed-oral-vascular-pulmonary-route-of-sars-cov-2-infection-and-the-importance-of-oral-healthcare-measures

Researchers have also noted that people with periodontitis are significantly more likely to experience complications from COVID-19. In fact, they quote another study which found that people with periodontitis were more likely to be admitted to intensive care units, need a ventilator, and die from the disease. At this time, it is not known for sure why this is, however the article postulates that it could have something to do with the fact that a constant viral load is being circulated to the lungs from the mouth. 

It is important to note that the assertions made in this article are still being researched. Currently, this is only a theory that requires additional studies to develop this idea further. With that being said, however, many dentists and medical professionals are advising people to stay caught up with their dental visits and daily oral hygiene routine to decrease the risk of periodontitis and potential complications of COVID-19. 


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Dr. Sanket Upadhyay


Dr. Sanket completed his Bachelor of Dental Surgery (BDS) degree in India in 2011 and obtained his Canadian dental license in 2016. He is a member in good standing with the Royal College of Dental Surgeons of Ontario, the Ontario Dental Association, and the Academy of General Dentistry. Dr. Sanket regularly pursues continuing education through dental conferences and courses to enhance his knowledge and be at the forefront of advances in dentistry.

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