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Microbiology · Respiratory RNA viruses

SARS-CoV-2 !

  • Virus
  • Enveloped
  • Contact
  • Airborne
  • Exam priority: high

The coronavirus behind COVID-19. It spreads through the air, mostly indoors, and can cause anything from a cold to severe pneumonia.

Updated 2026-11-01

Also called: COVID-19 coronavirus, novel coronavirus

At a glance

Shape
Spherical with a crown of spikes
Genome
Single-stranded, positive-sense RNA
Envelope
Enveloped
Family
Coronaviridae, genus Betacoronavirus
Size
About 60 to 140 nm

Morphology

  • Enveloped virus with the spike (S) protein, which binds the ACE2 receptor
  • One of the largest RNA genomes, with partial proofreading
  • Successive variants with spike mutations

Transmission

  • Respiratory particles and aerosols from breathing, talking, coughing or sneezing
  • Higher risk with close contact and poorly ventilated indoor spaces
  • Contaminated surfaces, of lesser importance
  • Spread possible before symptoms or without them

Reservoir: Humans; probable origin in bats

Isolation precautions

What the care team adds to standard precautions.

Contact
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.
Airborne
N95 respirator and a negative-pressure room.

Virulence factors

  • Spike binds ACE2 and the protease TMPRSS2 activates fusion
  • Damage to alveolar epithelium and endothelium, with microvascular thrombosis
  • Dysregulated inflammatory response in severe disease

Diseases it causes

Clinical picture

  • Incubation 3 to 6 days
  • Fever, chills, sore throat, cough, fatigue, headache; loss of smell or taste
  • Pneumonia with hypoxaemia and acute respiratory distress syndrome
  • Post-COVID condition with fatigue, breathlessness and poor concentration
  • Higher risk with older age and chronic disease

Diagnosis

  • RT-PCR of a nasopharyngeal swab
  • Rapid antigen tests, useful in the first days of symptoms
  • X-ray or CT: bilateral, peripheral ground-glass opacities
  • Lymphopenia, raised D-dimer and C-reactive protein in severe disease

Treatment

Antivirals for people at risk with early illness: main protease inhibitors (nirmatrelvir boosted with ritonavir) and nucleotide analogues (remdesivir). In severe disease with hypoxaemia, corticosteroids (dexamethasone) and immunomodulators such as interleukin-6 inhibitors are used.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Vaccination, which reduces severe disease, hospital stays and death
  • Ventilation, masks in risky situations and hand hygiene
  • In hospital: N95 respirator, eye protection, gown and gloves

Vaccine: Several vaccines (mRNA, viral vector, protein subunit and inactivated); Colombia vaccinated at scale from 2021 and now prioritizes the highest-risk groups.

Test yourself

Think of the answer, then tap the question to see it.

Which cell receptor does the SARS-CoV-2 spike protein bind?

Angiotensin-converting enzyme 2 (ACE2).

Which COVID-19 patients receive dexamethasone?

Those with severe disease and hypoxaemia or needing oxygen; not mild cases.

What protective equipment is recommended when caring for a COVID-19 patient?

An N95 or higher respirator, eye protection, gown and gloves, on top of standard precautions.

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← Back to the group: Respiratory RNA viruses

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Coronavirus disease (COVID-19) (World Health Organization (WHO), 2025); Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions (CDC, 2024).

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Representative model, for educational purposes only.