COVID-19, caused by the virus SARS-CoV-2, has now been established as a global pandemic; with established risk factors being age (mean age 69 years), gender (Males-70%), obesity (48% in people with BMI over 30kg/m2) and presence of other systemic diseases like diabetes (19%), hypertension (30%) and cardiovascular disease (8%). This makes us contemplate if there is a link between poor oral hygiene and COVID-19 infection; as there have been a substantial number of death reports (52%) amongst healthy individuals.
The correlation between Poor Oral Hygiene and COVID-19 Infection Risk
Even though COVID-19 is a viral infection, bacterial superinfections could be a contributory factor resulting in complications of pneumonia and acute respiratory distress syndrome (ARDS). The other paramount manifestations following this infection are blood clots, pneumonia, sepsis, and septic shock.
The COVID-19 patients have been seen to have an anomalously overwhelming immune response which leads to overproduction of pro-inflammatory cytokines such as (tumor necrosis factor-alpha (TNF- α], interleukins (IL-6, and IL-1β)); thus producing a state called ‘cytokine storm’. , The IL-6 levels are seen to be higher in the deceased as compared to the survivors.  As a result of this cytokine overkill these patients have an increased risk of vascular hyperpermeability and multi-organ failure, especially involving the heart and kidneys. 
As comprehended earlier in cases of influenza pandemic -1918 or during the 2009 -H1N1 influenza pandemic and the recent COVID-19 infection; ARDS still remains the primary cause of death in these patients.  It is common that patients suffering from respiratory viral infections become predisposed to bacterial superinfections; which ultimately lead to increased disease severity and death. Some species of the coronavirus have been shown to enhance streptococcal adherence to epithelial cells lining the respiratory tract, resulting in pneumonia and inflammatory damage within the lungs that inhibit bacterial clearance. 
Poor oral hygiene represented as periodontal disease is one of the most common ailments of bacterial origin in mankind. Periodontal disease has been proven to contribute to systemic inflammation and have severe implications in cases of cardiovascular disease, diabetes, renal and autoimmune diseases and even in chronic obstructive pulmonary disease (COPD).
This again brings us back to our question – does poor oral hygiene and covid-19 infection risk have a co-relation? A recent paper by Sampson et al, tried to explore the connection between high bacterial load in the mouth and post-viral complications. They also tried to comprehend if improving oral health could reduce the risk of complications from COVID-19.
Periodontal disease has been proven to be a nidus for bacterial transfer to the airway as seen in patients with COPD.  Inhalation of microorganisms embodied in aerosolized droplets, or by aspiration of oral secretions associated with the oral disease lead to infection of the lower respiratory tract epithelium. viii Periodontitis and tooth decay are the most common oral disorders related to bacterial imbalance in the mouth. It has been proven that periodontitis patients have increased production of proinflammatory cytokines IL-1 and TNF-α both in the gingival crevicular fluid (GCF) and blood. These cytokines in the GCF could be aspirated causing inflammation or infection in the lungs.,
The periodontal pathogens like F. nucleatum, P. gingivalis and P. intermedia which get aspired into the lungs have been proven to induced severe pneumonia. Besides the physical presence of bacteria, the enzymes associated with periodontal disease could modify the mucosal surfaces and aid in adhesion and colonization of respiratory pathogens; along with the destruction of the salivary pellicles on bacteria to delay their clearance from mucosal surfaces. The respiratory epithelium could also be altered by cytokines released due to periodontal infections which promotes infection by respiratory pathogens., ,  Thus, all these involved mechanisms hints that there could be an association between poor oral hygiene and COVID-19 infection.
Since there is a proven link between periodontal disease and systemic inflammation; this plausible connection between poor oral hygiene and COVID-19 infection should be further explored. As dental practitioners, we must try and ensure that we are aware of this possible scenario and try to inculcate good oral hygiene practices amongst our patients.
 World Health Organisation. Coronavirus disease (COVID-19) pandemic. 2020. Available online at https://www.who.int/emergencies/diseases/novel-coronavirus-2019 (accessed July 2020).
 Zhou F, Yu T, Du R et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospectove study. Lancet 2020; 395: 1054-1062.
 World Health Organisation. Clinical Management of severe acute respiratory infection when novel coronavirus (2019-nCoV) infection is suspected. 2020. Available online at https://apps.who.int/iris/handle/10665/330893 (accessed June 2020).
Jose R J, Manuel A. COVID-19 cytokine storm: the interplay between inflammation and coagulation. Lancet Respir Med2020; DOI: 10.1016/S2213-2600(20)30216-2.
 Tay M Z, Poh C M, Rénia L, MacAry P A, Ng L F P. The Trinity of COVID-19: Immunity, Inflammation and Intervention. Nat Rev Immunol 2020; 20: 363-374.
 Wu C, Chen X, Cai Y et al. Risk Factors Associated with Acute Respiratory Distress Syndrome and Death in Patients With Coronavirus Disease 2019 Pneumonia in Wuhan, China. JAMA Intern Med 2020; DOI: 10.1001/jamainternmed.2020.0994.
 Golda A, Malek N, Dudek B et al. Infection with human coronavirus NL63 enhances streptococcal adherence to epithelial cells. J Gen Virol 2011; 92: 1358-1368.
 Scannapieco F A. Role of Oral Bacteria in Respiratory Infection. J Periodontol 1999; 70: 793-802.
 Sampson, V., Kamona, N. & Sampson, A. Could there be a link between oral hygiene and the severity of SARS-CoV-2 infections?.Br Dent J 228, 971–975 (2020).
 Scannapieco F A, Genco R J. Association of periodontal infections with atherosclerotic and pulmonary diseases. J Periodontal Res1999; 34: 340-345.
 Nagaoka K, Yanagihara K, Morinaga Y et al. Prevotella intermedia Induces Severe Bacteraemic Pneumococcal Pneumonia in Mice with Upregulated Platelet-Activating Factor Receptor Expression. Infect Immun 2014; 82: 587-593.
 Hayata M, Watanabe N, Tamura M. The Periodontopathic Bacterium Fusobacterium nucleatum Induced Proinflammatory Cytokine Production by Human Respiratory Epithelial Cell Lines and in the Lower Respiratory Organs in Mice. Cell Physiol Biochem2019; 53: 49-61.