Open a can of soda and spread a virus around the world that no one knows how to get rid of.
If the image surprises, the study by Christian Yates, lecturer in biomathematics at the University of Bath, in the United Kingdom, makes it plausible: the total volume of SARS-CoV-2 coronavirus present in the world does not would not exceed, according to him, 120 ml.
That's less than half (330ml) of a can of regular soda.
As surreal as it is, this study, popularized by its author in the online media The Conversation, attempts to calculate the volume of Covid-19 on the basis of concrete data ... but also of estimates.
Christian Yates recognizes in the preamble, his work, "largely perfectible", is "an approximation based on the most" reasonable "assumptions".
READ ALSO>
Covid-19: follow our direct
However, it is certain that even taking into account the highest figures would make it possible to arrive at a volume in these same proportions.
"Even if we base our calculations on the highest estimated value for the diameter of a viral particle," he remarks, "all the SARS-CoV-2 on the planet would still not be enough to fill a can of soda. !
"
Assumed approximations, intact scientific rigor
To complete his study, Christian Yates began by estimating the number of SARS-CoV-2 particles present on the planet.
He started with the number of infected humans: 3 million per day, taking into account the number - also estimated - of asymptomatic cases, according to figures from the Institute for Health Data and Assessments, based in Seattle in the USA.
This takes into account the value of the viral load, fluctuating during the course of the disease, with a peak located around the sixth day.
Viral loads at the time of this peak range from 1 billion to 100 billion particles, according to a study conducted on monkeys, then adapted to the human species.
"At any given time, there are about two hundred quadrillons (two hundred million billion) of viral particles in the world," concludes Christian Yates.
READ ALSO>
Covid-19: is the cold spike slowing the Covid-19 epidemic?
“This number seems very large.
And it is, continues the scientist.
It more or less corresponds to the number of grains of sand present on our planet ”.
But that's without counting on the tiny size of the SARS-CoV-2 particles: an average diameter of 100 nanometers (
Editor's note
, a nanometer being one billionth of a meter).
“If we assume that a SARS-CoV-2 particle has a radius of 50 nm, the volume of a viral particle is 523,000 nanometers3”, illustrates Christian Yates at the end of his demonstration.
Morning essentials newsletter
A tour of the news to start the day
Subscribe to the newsletterAll newsletters
"By multiplying this tiny volume by the very large number of particles that we calculated above, and by converting the result into a more evocative unit of volumes, such as the milliliter, we obtain 120 ml", he concludes with an apparent ease.
This news may be shocking, but the image of the soda can alone makes the health situation a little more dizzying.