Covid

Basics

Description

  • Viral respiratory syndrome:
    • Can cause respiratory failure
    • Severe cases can result in cardiac arrhythmia, shock, thromboembolic events, encephalopathy, inflammatory response, and serious secondary infections
  • Results in a wide array of symptoms, most serious is respiratory failure
  • Similar to other viral upper respiratory tract infections
  • Transmitted via aerosols
  • Incubation period is within 14 d of exposure, most commonly within 5 d following an exposure
  • Transmission is most common in the first 7 d of illness and unlikely after 10 d of symptoms
  • Duration is highly variable with most infections lasting less than 14 d
  • “Long COVID” describes a poorly understood phenomenon in which an infected individual has persistent symptoms for many months following the acute phase

Epidemiology

  • Resulted in worldwide pandemic starting in 2019
  • 766 million confirmed cases worldwide as of May 2023
  • 6.9 million deaths globally as of May 2023

Etiology

  • Enveloped positive-sensed, single-stranded RNA virus:
    • SARS-CoV-2 is a betacoronavirus similar to severe acute respiratory syndrome virus (SARS) and Middle Eastern respiratory syndrome virus (MERS)
  • The host cell entry receptor is angiotensin-converting enzyme 2 (ACE-2):
    • The virus binds the receptor via a spike protein
    • Cell entry involves a protease cleaving the spike protein in order to enable membrane fusion
    • Cell entry is variant specific and Omicron viruses enter via cathepsin-dependent endocytosis
  • Variant nomenclature:
    • The World Health Organization (WHO) has designated labels based on the Greek alphabet:
      • Each variant has differences in transmissibility and pathogenesis

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