**2. Origin and pathophysiology aspects of COVID-19**

*SARS-CoV-2* was firstly discovered in the Huanan Seafood Wholesale market in Wuhan, China on 12 December 2019 [7]. Subsequent to the extensive outbreak of the virus infection, on March 11, 2020, the World Health Organization (WHO) announced the COVID-19 pandemic. As of 27 August 2021, the total number of cases of *SARS-CoV-2* confirmed globally by WHO are 214,468,601 with 4,470,969 reported deaths (https://covid19.who.int/). As per the reports of WHO, the mortality rate of COVID-19 is around 3.7% [8]. Although the host of *SARS-CoV-2* is still indistinct, it is assumed the virus has bats or pangolins origin. However, the main theory suggests that the virus was transmitted to humans from an intermediate host. The virus is mainly transmitted among the individuals through droplet infection, contact routes, and rarely through the feces of the infected patients and mother to child postchildbirth. Fever, cough, fatigue, diarrhea, headache, hemoptysis, dyspnea, acute respiratory distress syndrome, cardiac injury, and lymphopenia are known clinical manifestations of COVID-19. COVID-19 infection can be divided into three phases including the virus replication and appearance of mild signs, the emergence of respiratory symptoms and simulation of the adaptive immune system responses, and the third phase causing hyper-inflammation. Expression of the ACE2 (angiotensinconverting enzyme 2) protein (as the major receptor molecule for the virus) by renal tubular cells, liver cells and testicular cells may the kidney, liver, and testicular tissue damages also observed in the COVID-19 patients [1, 9, 10].
