Great Courses Professor Explains Characteristics of Novel Coronavirus

dr. barry fox explains size and transmissibility of novel coronavirus

By Jonny Lupsha, Wondrium Staff Writer

Health experts continue to study the novel coronavirus for new information. While no vaccine or cure has been developed, as of yet, our understanding of the virus is advancing. A Great Courses professor gives us the latest update.

Scientists conducting research on Covid 19 virus in laboratory
Scientists worldwide continue to study and research further findings about the novel coronavirus and its transmissibility of spreading infection. Photo by Mongkolchon Akesin / Shutterstock

Dr. Barry C. Fox is a Clinical Professor of Infectious Disease at the University of Wisconsin School of Medicine and Public Health who earned his M.D. from Vanderbilt University. He’s also the professor for The Great Courses series An Introduction to Infectious Diseases. With an expert’s knowledge about the novel coronavirus, SARS-CoV-2 that causes COVID-19, he recently spoke at length with us about the virus and answered questions many people are asking about it.

SARS-CoV-2: Size and Transmissibility

Part of learning how the coronavirus spreads involves understanding just how small it really is. Dr. Fox said it’s really a very tiny particle.

“When we think of the air and we think of dust particles, dust particles in the air are about three microns in size,” he said. “A micron is one-millionth of a millimetre, and the actual virus itself is less than one micron in size. We think it’s 0.25 microns, which is pretty small.”

In other words, 12 copies of the virus, placed end to end, could fit on one dust particle.

Aerosol Droplets

Dr. Fox said that the coronavirus is spread by aerosol particles and by fomites. He explained aerosol particles first. They come from the lungs, but not just from coughing.

“When people speak, when people sing, they can generate force from inside their lungs and there are small amounts of moisture that are generated from inside the lung,” he said. “The virus kind of hitches a ride along these water droplets and other types of particles that are expelled from inside the lungs or from breathing through the nose, and the virus can then spread beyond the individual person.”

Dr. Fox said that the general findings are that the coronavirus can travel up to about six feet; but since it’s attached to an aerosol droplet, the weight of the droplet brings the virus down to the ground by the time it can travel any further. This is why social distancing comes with a recommended six-foot radius between any two people. In some exceptional cases—in a “choir type of circumstance” or with someone shouting, he said—the aerosol droplets can travel up to 10 feet.


“When the particles hit the ground, or hit the table, they’re kind of relabeled, so instead of aerosols, they’re called fomites, which are basically the same kind of material,” Dr. Fox said. “So the next question is, ‘If I touch a fomite, am I going to get infected?’ And the answer is no, unless you also take what you touch and you touch your face—more specifically, if you touch the mucous membranes of the eyes, the nose, or inside the mouth.”

Dr. Fox said the virus doesn’t spread through intact skin. In other words, it doesn’t burrow through the skin like battery acid; it has to touch a sensitive part of your face. This explains why health experts are advising people to consciously avoid touching their faces, which we do on average six times per hour.

With U.S. coronavirus cases recently passing the 3-million mark, it’s important to separate fact from fiction and get proper information. The Great Courses will continue to publish COVID-19 facts as they become available.

Image of Professor Barry Fox, M.D.

Dr. Barry Fox contributed to this article. Dr. Fox is a Clinical Professor of Infectious Disease at the University of Wisconsin School of Medicine and Public Health. He received his undergraduate degree in Molecular Biophysics and Biochemistry from Yale University and his medical degree from Vanderbilt University. He is board certified in both Internal Medicine and Infectious Disease.