What is SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2)?

SARS-CoV-2: The Virus Behind COVID-19

SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) is a novel zoonotic coronavirus that causes COVID-19, an acute respiratory illness that has resulted in a global pandemic with significant morbidity and mortality. 1

Viral Characteristics

• SARS-CoV-2 is a member of the pathogenic Coronaviridae family, which are enveloped positive-sense single-stranded RNA viruses 1
• It belongs to the Betacoronavirus genus, the same group as SARS-CoV (which caused the 2003 SARS outbreak) and MERS-CoV 1
• SARS-CoV-2 shares approximately 76.9% genetic homology with the original SARS-CoV-1 virus 1
• The virus likely originated from an animal reservoir, with bats being the most probable source 1, 2

Mechanism of Infection

• SARS-CoV-2 primarily enters human cells by binding to angiotensin-converting enzyme 2 (ACE2) receptors 1
• ACE2 receptors are expressed in multiple tissues including:
  • Respiratory epithelial cells (primary site of infection) 1
  • Vascular endothelial cells 1
  • Gastrointestinal epithelial cells 1
  • Kidney proximal tubular cells 1
  • Cardiac myocytes 1
• Unlike other common respiratory pathogens that use protein-linked sialic acid as receptors, SARS-CoV-2 specifically targets ACE2, which may contribute to its unique pathophysiology 1

Clinical Manifestations

• COVID-19 presents with a spectrum of clinical manifestations ranging from asymptomatic to severe disease 1
• Common symptoms include:
  • Fever 1
  • Cough 1
  • Shortness of breath 1
  • Fatigue 1
  • Body aches 1
  • Loss of taste or smell 1
  • Sore throat 1
• In severe cases, patients may develop:
  • Pneumonia 1
  • Acute respiratory distress syndrome (ARDS) 1
  • Cytokine storm (hyperinflammatory state) 1
  • Multi-organ dysfunction 1

Neurological Involvement

• SARS-CoV-2 can cause neurological manifestations through:
  • Direct viral invasion of neural tissue 1
  • Immune-mediated damage 1
  • Hypoxic injury 1
• Reported neurological complications include:
  • Meningoencephalitis 1
  • Viral-associated necrotizing encephalopathies 1
  • Cytokine-induced acute necrotizing syndromes 1

Liver Involvement

• Abnormal liver function can occur in patients with COVID-19 1
• Liver derangement may present as:
  • Hepatitis 1
  • Cholestasis 1
  • Elevated alanine aminotransferase (ALT) (reported in 28% of patients in early studies) 1
  • Increased total bilirubin (reported in 18% of patients) 1
• Liver dysfunction severity typically correlates with COVID-19 severity 1
• Liver histology shows microvascular steatosis, syncytial multinuclear hepatocytes, and mild lobular and portal activity 1

Transmission

• SARS-CoV-2 spreads primarily through:
  • Human-to-human transmission via respiratory droplets 1, 3
  • Direct contact with infected individuals 3
  • Potentially through aerosols (under investigation) 1
• The virus has been detected in:
  • Respiratory secretions 1
  • Feces 1
  • Wastewater (enabling wastewater-based epidemiology as a surveillance tool) 1
• The estimated basic reproduction number (R₀) is 2.24-3.58, indicating high transmissibility 3
• Mean incubation period is approximately 6.4 days 3

Diagnosis

• The gold standard for diagnosis is reverse transcription polymerase chain reaction (RT-PCR) testing 1
• Other detection methods include:
  • Digital droplet RT-PCR (ddRT-PCR) 1
  • Multiplex PCR 1
  • RT-LAMP (Loop-mediated isothermal amplification) 1
  • Electrochemical immunosensors 1

Treatment

• There is currently no specific universally effective treatment for COVID-19 1, 2
• Management primarily involves:
  • Supportive care 1
  • Oxygen therapy for respiratory symptoms 1
  • Antiviral therapy in selected cases 1
• Remdesivir, an antiviral drug, is FDA-approved for treatment of COVID-19 in:
  • Hospitalized patients 4
  • Non-hospitalized patients with mild-to-moderate COVID-19 who are at high risk for progression to severe disease 4
• Immunomodulatory agents may be beneficial in severe cases with cytokine storm 1

Global Impact

• As of April 2023, there have been over 763 million reported cases of COVID-19 worldwide with over 6.9 million deaths 1
• The pandemic has caused significant disruptions to healthcare systems, economies, and social structures globally 1

Prevention

• Preventive measures include:
  • Vaccination 5
  • Social distancing 1
  • Proper hand hygiene 1
  • Use of face masks 1
  • Isolation of infected individuals 1
• Wastewater surveillance has emerged as an important epidemiological tool for monitoring community spread 1