1. Pathogenesis:
The coronaviruses genome structure is best known among all RNA viruses of virosphere. Two-third (2/3) part of their genome (RNA) encodes for the viral polymerases (RdRp), material responsible for RNA synthesis, and two (Ⅱ) big structural polypeptides are responsible for the host immune responses modulation (ORF1a-ORF1b). The remaining one-third (1/3) part of RNA encodes for four (IV) structural proteins. These structural proteins include spike (S) proteins, envelop (E) proteins, membrane (M) proteins, and nucleocapsid (N) proteins (Shereen et al., 2020). COVID-19 causes the infection of lower respiratory tract of human and results in pneumonia (Zhong et al., 2003). Patients infected with COVID-19 had the higher leukocyte count, respiratory abnormalities, and elevated levels of plasma proinflammatory cytokines (Cui, Li, & Shi, 2019). Few patients can also face headache or hemoptysis and even relatively asymptomatic. According to Li et al; patients suffering from COVID-19 develop diarrhea (Klopfenstein et al., 2020) with loss of taste and smell (Menni et al., 2020). Coronavirus causes approximately 15% of adult common colds while the same strains of coronaviruses can cause debilitation and pneumonia in immunocompromised older adults (Nikolich-Zugich et al., 2020). Affected aged individuals with medical findings have a greater chance of respiratory failure due to severe lungs “alveolar” damage (Adhikari et al., 2020). These signs and symptoms are analogous with SARS-CoVs and MERS-CoVs infections. The bases of initial infections with SARS-CoV-2 are not completely known until now. Although, pathogenesis mechanism of COVID-19 is inadequately learnt, however, the same mechanism of SARS-CoVs and MERS-CoVs can provide us huge information about the SARS-CoV-2 pathogenesis. Similarly, the attachment of SARS-CoV-2 with lung cells through ACE2 receptors lead to extended production of ACE2, which may catalyze the destruction of host alveolar cells. Injury to human alveolar cells run a group of systemic reactions and even death occurres (Hoffmann et al., 2020) as shown in figure 1. Generally, the coronavirus infection consists on attachment, entry, replication, translation, virion assembly and release of virus (Hoffmann et al., 2020) (Shirato, Kawase, & Matsuyama, 2018).