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).