COVID-19

COVID-19 AKA WUHAN virus is caused by SARS COV 2, which was declared pandemic on FEBRUARARY 11, 2020 by WHO.

Family    –  Coronaviridae

Genus     –  Beta Coronavrus (SARS COV 2)

Suborder –  Coronavirinae

Order      –   Nidovirales

Realm     –   Ribavirin- Group of viruses having RNA dependent RNA Polymerase (RDRP)      

It is a type of Zoonotic virus, which means it is likely to originate from animals most probably from bats.

Morphology of SARS COV 2

It is spherical shape and enveloped by club shaped spike. It’s diameter is 100-150nm. it’s outermost membrane is covered by club shaped spike projections (coded by S Gene).

Genome

It’s genome is composed of non- segmented, positive sense single strnded RNA. The size of genome is large about 30 kbs.

It’s genome contains genes for

• Structural proteins
• Envelope                         – coded by E gene
• Nucleocapsid protein      – coded by N gene
• Membrane Glycoprotein – coded by M gene
• Accessory proteins

MODE OF TRANSMISSION

• Spreads through infected droplets
• Aerosol spread is more efficient route of transmission
• Contact transmission
• It spreads through stool contamination, plasma, serum
• Maximum shedding of occurs within 5-8 hours before onset of symptoms
• Virus is culturable and can be isolated for next 6-8 days

Patient can be considered non infectious after 2 weeks of symptoms onset

PATHOGENESIS

Virus enters upper respiratory tract(URI) and binds to specific receptor present in lungs and that receptor is ACE 2 receptor(Angiotensin converting enzyme). Initially in asymptomatic phase (1-2 days) virus binds to ACE 2 receptors present in human airway with the help of receptor binding domain of spike protein. This leads to confirmational change and fusion of virus and host cell membrane. Following this Type 2 Transmembrane Serine protease(TMPR SS2) present on surface of host cell clears these ACE 2 receptors and further activate the spike glycoprotein of SARS COV2. This leads to confirmation changes in the host cell, due to which the virus enters into the host cell. Then, the uncoating of the viral particle occurs by releasing of Nucleic acid in cytoplasm and Further replication and Translation in nuclei. Upon completion of machinery, the virus gets assembled in cytoplasm and released by Exocytosis. These new viral particles further attack new cells

Clinical Feature

80% of infected person develop mild disease. 20% of infected person develop moderate to severe disease. These 20% may need oxygen therapy or ventilation support.