Background: SARS-CoV-2, the virus responsible for the current COVID-19 infection pandemic, has caused substantial damage and negative impacts in the world, including physical sickness, mental illness, death, society lock down, work interruption, and productivity reduction. From the onset in early 2020, the pandemic has not yet totally subsided as of July 2022. Although great efforts have been made to understand the nature of this pandemic by the medical and scientific communities, a comprehensive review of this pandemic has not been reported. Purpose: We aimed to perform a thorough review of the subject in order to come to a better understanding of the origin of the virus, its mutations and their corresponding health effects, its pathophysiology, and its responses to therapeutic intervention. A more comprehensive set of data on these subject matters, if available, would give healthcare providers a valuable tool in formulating the best methods to respond to the current disease and prevent the disease from spreading in the future. Method: An extensive literature search on the subjects of COVID-19 was conducted regarding the possible origin of the viral pathogen, its evolutionary changes and health impacts, the world's responses to COVID-19 and outcomes of their responses, and healthcare professional's actions to understand and manage the disease and the results of their actions. To gather these data, websites of PubMed and Google Scholar were utilized for the search with the following keywords: Pandemic, COVID-19, coronavirus, SARS, SARS-CoV, SARS-CoV-2, origin, pathogenesis, and treatment. Results: Our review revealed data that How to cite this paper: Nguyen, V.T. and Chan, L.S. (2022) COVID-19 Infection: The Virus and Its Origin, the Variants, the Immune Defense, the Multiorgan Autoimmune Reactions, and the Targeted Treatments. Advances in Infectious Diseases, 12, 568-631.