medicalexpress | Scientists have known for several months the new coronavirus can become
suspended in microdroplets expelled by patients when they speak and
breathe, but until now there was no proof that these tiny particles are
infectious.
A new study by scientists at the University of Nebraska that was
uploaded to a medical preprint site this week has shown for the first
time that SARS-CoV-2 taken from microdroplets, defined as under five
microns, can replicate in lab conditions.
This boosts the hypothesis that normal speaking and breathing, not
just coughing and sneezing, are responsible for spreading COVID-19—and
that infectious doses of the virus can travel distances far greater than
the six feet (two meters) urged by social distancing guidelines.
The results are still considered preliminary and have not yet
appeared in a peer-reviewed journal, which would lend more credibility
to the methods devised by the scientists.
The paper was posted to the medrxiv.org website, where most
cutting-edge research during the pandemic has first been made public.
The same team wrote a paper in March showing that the virus remains
airborne in the rooms of hospitalized COVID-19 patients, and this study
will soon be published in a journal, according to the lead author.
"It is actually fairly difficult" to collect the samples, Joshua
Santarpia, an associate professor at the University of Nebraska Medical
Center told AFP.
The team used a device the size of a cell phone for the purpose, but
"the concentrations are typically very low, your chances of recovering
material are small."
The scientists took air samples from five rooms of bedridden patients, at a height of about a foot (30 centimeters) over the foot of their beds.
The patients were talking, which produces microdroplets that become
suspended in the air for several hours in what is referred to as an
"aerosol," and some were coughing.
The team managed to collect microdroplets as small as one micron in diameter.
They then placed these samples into a culture to make them grow,
finding that three of the 18 samples tested were able to replicate.
For Santarpia, this represents proof that microdroplets, which also
travel much greater distances than big droplets, are capable of
infecting people.
"It is replicated in cell culture and therefore infectious," he said.
