Lung nontumor
OLD Coronavirus disease 2019 (COVID-19)

Topic Completed: 7 April 2020

Minor changes: 4 August 2020

Copyright: 2020,, Inc.

PubMed Search: COVID-19[TI] lung

See Also: COVID-19 testing topic

Akira Yoshikawa, M.D.
Andrey Bychkov, M.D., Ph.D.
Page views in 2020 to date: 8
Cite this page: Yoshikawa A, Bychkov A. OLD COVID-19. website. Accessed August 13th, 2020.
Definition / general
  • Coronavirus disease 2019 (COVID-19) is an infectious respiratory disease caused by a novel coronavirus that emerged in Wuhan, China at the end of 2019, resulting in a worldwide pandemic
Essential features
  • COVID-19 can progress to severe acute respiratory syndrome with pneumonia and acute respiratory distress syndrome
  • The disease spreads rapidly and became a global outbreak approaching 1 million cases at the start of April 2020
  • Definite diagnosis is based on detection of viral RNA by RT-PCR
  • Histologically, COVID-19 shows diffuse alveolar damage corresponding to the phase of the disease (acute to fibrotic)
  • COVID-19 is also called novel coronavirus pneumonia
  • Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is also called 2019 novel coronavirus (2019-nCoV)
ICD coding
  • ICD-10 (emergency codes):
    • U07.1 - COVID-19 confirmed by laboratory testing
    • U07.2 - suspicious for COVID-19 with inconclusive laboratory testing
  • ICD-11:
    • RA01.0 - COVID-19 (definite)
    • RA01.1 - COVID-19 (suspected or probable)
  • Upper respiratory tract in mild disease
  • Bilateral lobes of the lung in more severe disease
  • Spike surface glycoprotein of the virus binds to the host via receptor binding domains of the angiotensin converting enzyme 2 (ACE2), which is most abundant in type II alveolar cells (J Virol 2020;94:e00127-20)
  • After a SARS-CoV-2 attaches to a target cell, the virion releases RNA into the cell, initiating replication of the virus which further disseminates to infect more cells (Cell 2020 Mar 4 [Epub ahead of print])
  • SARS-CoV-2 produces several virulence factors that promote shedding of new virions from host cells and inhibit immune response
  • Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a positive sense, single stranded RNA virus having close genetic similarity to bat coronaviruses (Nature 2020;579:270)
Diagrams / tables

Images hosted on other servers:


Epidemic timeline of COVID-19 in China

Clinical features
Radiology description
Radiology images

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Chest CT images

Severe changes

Prognostic factors
Case reports
Gross description
Gross images
  • Not available
Microscopic (histologic) description
  • Pulmonary changes are the most significant, although nonspecific (Lancet Respir Med 2020 Feb 18 [Epub ahead of print], J Thorac Oncol 2020 Feb 28 [Epub ahead of print], Preprints 2020;2020030311)
    • Findings of diffuse alveolar damage corresponding to the phase of disease
      • Exudative phase: hyaline membrane formation, desquamation of pneumocytes, cellular or proteinaceous exudates, alveolar hemorrhage, fibrinoid necrosis of small vessels
      • Organizing phase: interstitial and intraalveolar proliferation of fibroblasts, lymphocytic infiltration, type II pneumocyte hyperplasia, fibrin deposition
      • Findings representing the fibrotic phase (e.g. dense collagenous fibrosis, architectural remodeling) are not reported so far
    • Viral infection changes
      • Multinucleated enlarged pneumocytes with large nuclei, amphophilic cytoplasm and prominent nucleoli in alveolar spaces
      • Intranuclear inclusions
    • Bacterial pneumonia may be superimposed
  • Extrapulmonary changes: various levels of cell injury and microvascular disorders in parenchymal organs (Zhonghua Bing Li Xue Za Zhi 2020;49:E009)
  • Pathological findings are primarily based on minimally invasive autopsies
Microscopic (histologic) images

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Lung, liver and myocardium

Diffuse alveolar damage

Marked alveolar hemorrhage

Cytology description
Cytology images

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BAL specimen

Positive stains
Negative stains
  • Not applicable
Electron microscopy description
  • Spherical particles sized 60 - 140 nm
  • Distinctive spikes on the surface (9 - 12 nm) giving virions the appearance of a solar corona, consistent with the Coronaviridae family
  • Inclusion bodies filled with virus particles in membrane bound vesicles in cytoplasm of the respiratory epithelium (N Engl J Med 2020;382:727)
Electron microscopy images

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Scanning electron microscopy

Transmission electron microscopy

Molecular / cytogenetics description

Histology of acute respiratory distress syndrome

First forensic report

Sample pathology report
  • Usually reported as part of autopsy findings:
    • Diffuse alveolar damage with changes compatible with viral infection
Board review style question #1

Which is the target organ affected by SARS-CoV-2 and responsible for the major manifestation of COVID-19?

  1. Brain
  2. Heart
  3. Kidney
  4. Liver
  5. Lung
Board review answer #1
Board review style question #2
Which of the following findings suggests viral infection of the lung?

  1. Alveolar hemorrhage

  2. Fibrin deposition
  3. Neutrophilic aggregation

  4. Nuclear inclusions
  5. Type II pneumocyte hyperplasia
Board review answer #2
D. Nuclear inclusions

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Reference: Coronavirus disease 2019 (COVID-19)
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