A number of Wuhan hospitals treated clusters of patients with pneumonia in late December 2019; the causes of these cases remain unknown. On January 30 The World Health Organization (WHO) recognized the ongoing coronavirus outbreak as a global public health emergency. The International Committee on Taxonomy of Viruses officially named the new coronavirus "SARS-CoV-2" on February 11, whereas the World Health Organization classified the disease as "COVID-19"." New research shows that SARS-CoV-2 uses the ACE2 receptor to access cells, working in tandem with the host's TMPRSS2. Research has discovered that cells that have a greater amount of ACE2 expression are more vulnerable to the SARS-COV S protein. This implies that higher levels of ACE2 could heighten the likelihood of SARS-CoV-2 infection. Although most coronaviruses affect birds, some can infect mammals as well.(2) Key stages in the infection process of SARS-CoV-2 in host cells involve the use of Ace2 and TMPRSS2.. As with other viruses, SARS-CoV-2 employs transmembrane serine protein 2 (TMPRSS2) as a major entry point into human cells.