A review on SARS-CoV-2: the origin, taxonomy, transmission, diagnosis, clinical manifestations, treatment and prophylaxis

Abstract

Coronavirus disease 19 (COVID-19) pandemic, caused by highly contagious SARS-CoV-2 that infects the respiratory system. COVID-19 started in Wuhan, south China, in December 2019, and spread to all other parts of the world. SARS-CoV-2 has +ssRNA genome (29,844bp) enclosed in an enveloped capsule (60 to 140 nm) and showing high genome homology (96%) with coronavirus of   its potential natural reservoir Horseshoe bats. Two types of SARS-CoV-2 were detected: type L (70%) and type S (30%). SARS-CoV-2 spikes have very high binding affinity with all cells expressing ACE2 receptor. Nasal swabs and bronchoalveolar lavage samples were used by reverse transcriptase rtPCR for detection of SARS-CoV-2. ELISA can detect anti-SARS-CoV-2 IgM and IgG antibodies five days post infection. COVID-19 infection is confirmed by clinical signs and symptoms and CT thoracic images. Patients typically present with fever (87.3%), cough (58.1%), dyspnea (38.3%), muscle soreness or fatigue (35.5%), chest distress (31.2%) and expectoration (29.4%). The fatality rate of the infection approaches 7%. Hundreds of lungs micro clots were reported to occur causing heart failure and death. Fatal consequences were reported in older patients and those with chronic diseases. There is no specific medicine, but supportive treatment and anticoagulants   are in use. Chloroquine and azithromycin have fatal consequences in 50% of patients, while Remdesivir did not show significant clinical or antiviral effects.  Plasma convalescence   clear the infection within three days. There is no vaccine for SARS-CoV-2 due to its mutations. Social isolation and countries lockdown measures exert catastrophic negative impact on health and economy worldwide.