Oral Infections, SARS-CoV-2 Infection, and Autoimmunity

Abstract

A new strain of virus, SARS-CoV-2, caused the coronavirus disease of 2019 (COVID-19) and became the greatest global health challenge. Even though most patients (over 80% of exposed patients) present mild symptoms, 13.8% developed severe diseases, namely pneumonia, sepsis, and acute respiratory distress syndrome (ARDS), and 6.1% reached a critical state requiring intensive care sometimes resulting in multi-organ failure or death [1,2]. Several pre-existing conditions have been associated with severe COVID-19 complications. These include, among others, older age, male sex, increased body mass index, diabetes mellitus with high levels of glycohemoglobin (HbA1c), cardiovascular diseases, cerebrovascular diseases, smoking, chronic kidney diseases, chronic lung diseases (particularly chronic obstructive pulmonary disease), hypertension, moderate-to-severe asthma, cancer, organ transplantation with immunosuppression, and pregnancy. [3,4] Some of these predisposing conditions increase the risk of COVID-19 complications through their ability to increase systemic inflammation (i.e., asthma and autoimmunity) and to promote the overexpression of ACE2 (in obesity), which favors virus binding, [5,6] or compromised immunity via obesity/diabetes [7], or pregnancy [8]. Other comorbidities compromising the respiratory system are COPD, smoking, and asthma [9,10]. Also, cancer, anemia, and sickle cell disease increase the risk of severe COVID-19 outcomes [11]. However, HIV or AIDS did not increase the risk of severe COVID-19 [12].