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 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 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.
The potential for microdroplet transmission of the coronavirus was acknowledged and it may be a possibility, which is the rationale for universal masking.
Visitors wearing face masks view exhibits in the West Building of the National Gallery of Art in Washington, D.C., the United States, July 20. Photo: Xinhua
