A researcher at the University of North Carolina School of Medicine has generated scanning electron microscopy images showing startlingly high SARS-CoV-2 viral loads on human bronchial epithelial cells.
Dr. Camille Ehre from the Baric and Boucher Laboratories at the University of North Carolina School of Medicine inoculated the SARS-Co-V-2 virus into human bronchial epithelial cells.
The inoculation was performed in a biosafety level 3 facility and had a multiplicity of infection — indicating the ratio of virus particles to targeted airway cells — of 3:1.
The cells were examined 96 hours after infection with the use of scanning electron microscopy (SEM).
The images show infected ciliated cells with strands of mucus (yellow) attached to cilia tips (blue).
Cilia are the hair-like structures on the surface of airway epithelial cells that transport mucus and trapped viruses from the lung.
A higher power magnification image shows the structure and density of SARS-CoV-2 virions (red) produced by human airway epithelia.
Virions are the complete, infectious form of the virus released onto respiratory surfaces by infected host cells.
“This imaging research helps illustrate the incredibly high number of virions produced and released per cell inside the human respiratory system,” Dr. Ehre said.
“The large viral burden is a source for spread of infection to multiple organs of an infected individual and likely mediates the high frequency of COVID-19 transmission to others.”
“These images make a strong case for the use of masks by infected and uninfected individuals to limit SARS-CoV-2 transmission.”
The work was published this month in the Images in Medicine section of the New England Journal of Medicine.
Camille Ehre. 2020. SARS-CoV-2 Infection of Airway Cells. N Engl J Med 383: 969; doi: 10.1056/NEJMicm2023328