The SARS-CoV-2 virus that causes Covid-19 is predominantly transmitted through air, according to a new assessment carried in the medical journal Lancet which said it found little to no evidence that the virus spreads easily via large droplets, which fall quickly through the air and contaminate surfaces.
The study added that public health measures that fail to treat the virus as predominantly airborne leave people unprotected and allow the virus to spread. The study observation is significant for India where mass gatherings and election rallies continue unabated even as overall Covid-19 cases are breaking records daily.
A multi-research team from the UK, the US and Canada warned that public health measures that fail to treat the virus as predominantly airborne leave people unprotected and allow the virus to spread.
Silent (asymptomatic or presymptomatic) transmission of SARS-CoV-2 from people who are not coughing or sneezing accounts for at least 40 per cent of all transmission.
This silent transmission is a key way Covid-19 has spread around the world, “supporting a predominantly airborne mode of transmission,” as per the assessment.
By contrast, the researchers found little to no evidence that the virus spreads easily via large droplets, which fall quickly through the air and contaminate surfaces.
“The evidence supporting airborne transmission is overwhelming, and evidence supporting large droplet transmission is almost non-existent,” said Jose-Luis Jimenez, a chemist at the Cooperative Institute for Research in Environmental Sciences (CIRES) and the University of Colorado Boulder.
“It is urgent that the World Health Organisation and other public health agencies adapt their description of transmission to the scientific evidence so that the focus of mitigation is put on reducing airborne transmission,” Jimenez said.
Further, the researchers emphasise that while it is necessary to wash hand and clean surfaces, they should be given less emphasis than airborne measures.
If an infectious virus is primarily airborne, someone can potentially be infected when they inhale aerosols produced when an infected person exhales, speaks, shouts, sings, or sneezes.
The airborne control measures include ventilation, air filtration, reducing crowding and the amount of time people spend indoors, wearing masks whenever indoors (even if not within 6 feet or two metres of others), attention to mask quality and fit, and higher-grade PPE for healthcare and other staff when working in contact with potentially infectious people.
The team reviewed published research and identified 10 lines of evidence to support the predominance of the airborne route.
Moreover, transmission rates of SARS-CoV-2 are much higher indoors than outdoors, and transmission is greatly reduced by indoor ventilation. The researchers also cited work demonstrating long-range transmission of the virus between people in adjacent rooms in hotels; people who were never in each other’s presence.