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A Close-up of COVID-19 in Lung Cells

Posted on by Dr. Francis Collins

SARS-CoV-2 infected lung cells
Credit: Ehre Lab, UNC School of Medicine

If you or a loved one have come down with SARS-CoV-2, the coronavirus responsible for COVID-19, you know it often takes hold in the respiratory system. This image offers a striking example of exactly what happens to cells in the human airway when this coronavirus infects them.

This colorized scanning electron microscope (SEM) image shows SARS-CoV-2-infected human lung cells (purple) covered in hair-like cilia (blue). Those cilia line the inner surface of the airways and help to clear mucus (yellow-green) containing dust and other debris from the lungs. Emerging from the surface of those infected airway cells are many thousands of coronavirus particles (red).

This dramatic image, published recently in the New England Journal of Medicine, comes from the lab of pediatric pulmonologist Camille Ehre, University of North Carolina at Chapel Hill. Ehre and team study mucus and how its properties change in cystic fibrosis, chronic obstructive pulmonary disease (COPD), and various other conditions that affect the lungs. These days, they’re also focusing their attention on SARS-CoV-2 and potentially new ways to block viral entry into cells of the human airway.

As part of that effort, she and her colleagues captured this snapshot of SARS-CoV-2 viruses exiting from lung cells in a lab dish. They first cultured cells from the lining of a human airway, then inoculated them with the virus. Ninety-six hours later, this is what they saw in greyscale. The vivid colors were added later by UNC medical student Cameron Morrison.

The image illustrates the astoundingly large number of viral particles that can be produced and released from infected human cells. Ehre notes that in a lab dish containing about a million human cells, they’ve witnessed the virus explode from about 1,000 particles to about 10 million in just a couple of days.

The dramatic increase in viral particles helps to explain how COVID-19 spreads so easily from the lungs to other parts of the body and—all too often—on to other individuals, especially in crowded, indoor places where people aren’t able to keep their distance. Hopefully, images like this one will help to inspire more of us this winter to avoid the crowds (especially indoors), wear masks, and wash our hands frequently.


[1] SARS-CoV-2 infection of airway cells. Ehre C. NEJM. 2020 Sep 3;383(10):969.


Coronavirus (COVID-19) (NIH)

Camille Ehre (University of North Carolina, Chapel Hill)


  • Camille Ehre says:

    Thank you, Dr. Collins, for mentioning our work. Can’t wait to publish our next paper on SARS-CoV-2 infection!

  • John Hasty BS MT(ASCP) Retired says:

    Which came first the green (pneumonia) or the red (virus)?

    • Camille Ehre says:

      Mucus (green) is always coating the airway cell surfaces. However, mucus production can be upregulated by viral infection or other stressors, like cigarette smoke. Paper in preparation to describe how SARS-CoV-2 (red) infection affects airway cells and mucus secretion.

  • Scott H. Donaldson says:

    Thanks for sharing these – and reminding us that wearing masks is more important today than ever, as we await the impact of vaccines in the coming months.

  • Lindsay W. says:

    Being a sever asthmatic I’m very afraid of contacting the covid virus. I wish the push for the vaccine were greater where I live. I’m 64 and very afraid to get sick. I want to be vaccinated.

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