Intestinal Microbiota in the SARS-CoV-2 Infection: What Is Known?

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the etiological agent of COVID-19, emerged last year in China and quickly spread to millions of people around the world. This virus infects cells in different tissues and causes pulmonary (e.g., pneumonia and acute respiratory distress syndrome), neurological, cardiovascular, and intestinal manifestations, which can be the result of a direct viral effect or secondary to endothelial, thrombotic, or immunological alterations. In this chapter, we discuss recent studies which highlighted the relevance of the intestinal microbiota for other infectious respiratory diseases. We present the "altered microbiota" (dysbiotic) as a point of connection between conditions that are risk factors for the development of severe forms of COVID-19. In addition, we describe the findings of recent studies reporting alterations of microbiota composition in COVID-19 patients and speculate on how this may impact in development of the disease.