Following months of speculation and disagreement in the health community, a team of researchers has found that Covid-19 is airborne and that current social distancing guidelines could lead to more exposures and outbreaks.
Confirmation of aerosol transmission, at distances of 6.5 and 15.7 feet (2 and 4.8 metres), was made by University of Florida experts in virology and aerosol science, according to a research paper published on the preprint server medRxiv.
Their study found for the first time that Sars-Cov-2 in the form of tiny droplets known as aerosols remained viable in the air, suggesting a risk of inhaling the virus near carriers who cough, sneeze and speak.
"The public health implications are broad, especially as current best practices for limiting the spread of Covid-19 centre on social distancing, wearing of face-coverings while in proximity to others and hand-washing," the researchers wrote.
"For aerosol-based transmission, measures such as physical distancing by six feet would not be helpful in an indoor setting, provide a false sense of security and lead to exposures and outbreaks."
The disagreement in scientific circles as to whether coronavirus could be transmitted through the air stems from the previous detection of viral RNA in aerosols, but failure to isolate a viable virus — the difference between genetic material versus the live virus.
Researchers say they are the first to successfully sequence the genomes of Sars-CoV-2 from an air sampling, which was taken in the hospital room of a newly admitted patient. The live virus strain from the air was identical to the strain from the patient.
After months of saying Covid-19 spread mostly through close personal contact and that airborne transmission was unlikely to occur outside a hospital setting, the World Health Organisation updated its stance in July to say it couldn't be ruled out and that more evidence was needed.
"Short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out," the WHO said in its latest advice from 9 July.
It came after 239 scientists published a paper in Clinical Infectious Diseases, titled 'It is time to address airborne transmission of Covid-19', calling for the recognition of aerosol transmission based on several lab studies and case reports.
Dr Linsey Marr, a Virginia Tech engineering professor with expertise in airborne transmission of viruses, said on Twitter that the University of Florida study appears to be a "smoking gun".
"In lay terms: This study confirms, unambiguously in my view, that virus in aerosols (small enough to travel several metres) is infectious. We have suspected this and now have evidence." Ms Marr, who was not involved in the study, said in a tweet. "If this isn't a smoking gun, then I don't know what is."