The COVID 19, Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV 2). The word Corona is of Latin origin Coronam means crown-like appearance due to the presence of spike-like glycoproteins on the envelope with a positive-single stranded RNA when viewed under an electron microscope. The virus belongs to the Order– Nidovirales, Family– Coronaviridae. The Sub-Family– Orthocoronavirinae has been further classified into four genera they are-
- Alphacoronavirus (alpha CoV)
- Betacoronavirus (beta CoV)-The one of the five genera is SARS-CoV2
- Gammacoronavirus (gamma CoV)
- Deltacoronavirus (delta CoV)
HUMAN INFECTING CORONAVIRUS
- Human Coronavirus-OC43 and Human Coronavirus-HKU1 and Human Coronavirus-229E, and Human Coronavirus-NL63. The former is of Betacoronavirus family and the latter is of Alphacoronavirus family. The infected person suffers from common colds and self-limiting upper respiratory infections in immunocompetent individuals. In immunocompromised subjects and the elderly, lower respiratory tract infections can occur.
- Other coronaviruses that infect humans are-SARS-CoV, SARS-CoV-2, and MERS-CoV. These cause epidemics with variable clinical severity featuring respiratory and extra-respiratory manifestations.
SARS-CoV-2 or COVID-19 belongs to Betacoronavirus. It is round or elliptic and often pleomorphic form with a diameter of 60–140 nm. SARS-CoV-2 is sensitive to ultraviolet rays and heat. It can be effectively inactivated by lipid solvents including ether (75%), ethanol, chlorine-containing disinfectant, peroxyacetic acid and chloroform except for chlorhexidine. A specimen collected from Wuhan, when studied it was found that 89% of the nucleotide was identical with Chiroptera i.e bats SARS-CoronavirusZXC21 and 82% with human SARS-COVID. Hence a new virus called SARS-CoV-2 came into existence. The CoV-2 is a single-stranded RNA genome contains 29891 nucleotides, encoding for 9860 amino acids. The study of the genetic structure suggests that SARS-CoV-2 probably evolved from a strain found in bats but ambiguity still lies in its origin is ambiguous. It is so because the intermediate host between the human and the bat is not known. Till now it is assumed that due to the absence of an intermediate host, the mutation in the original strain may have directly triggered virulence towards humans.