There is consistent, strong evidence to prove that the SARS-CoV-2 virus, behind the Covid-19 pandemic, is predominantly transmitted through the air, according to a new assessment published on Friday in The Lancet journal.
The analysis by six experts from the UK, the US and Canada said public health measures that fail to treat the virus as predominantly airborne leave people unprotected and allow the virus to spread. “The evidence supporting airborne transmission is overwhelming, and evidence supporting large droplet transmission is almost non-existent,” said Jose-Luis Jimenez, from the University of Colorado Boulder in the US.
The researchers highlighted the super-spreader events such as last year’s Skagit Choir outbreak in the US, in which 53 people became infected from a single infected case.
Studies have confirmed these events cannot be adequately explained by close contact or touching shared surfaces or objects, the researchers said in their assessment. They noted that transmission rates of SARS-CoV-2 are much higher indoors than outdoors, and transmission is greatly reduced by indoor ventilation.
The team cited previous studies estimating that silent — asymptomatic or pre-symptomatic — transmission of SARS-CoV-2 from people who are not coughing or sneezing accounts for at least 40% of all transmission.
The researchers also highlighted work demonstrating long-range transmission of the virus between people in adjacent rooms in hotels, who were never in each other’s presence. On the contrary, the team found little to no evidence that the virus spreads easily via large droplets, which fall quickly through the air and contaminate surfaces.
The assessment has serious implications for public health measures designed to mitigate the pandemic, the researchers said. They said “droplet measures” such as handwashing and surface cleaning, while important, should be given less emphasis than airborne measures, which deal with inhalation of infectious particles suspended in the air.
According to the researchers, 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. They noted that some airborne control measures include ventilation, air filtration, reducing crowding and the amount of time people spend indoors.
Wearing masks whenever indoors, attention to mask quality and fit, and higher-grade PPE for healthcare and other staff when working in contact with potentially infectious people are some of the other control measures, according to the researchers.(Courtesy the Hindu)
