Thereis consistent, strong evidence to prove that the SARS-CoV-2 virus, which causesCovid-19, is predominantly transmitted through the air, according to a newassessment published in the medical journal The Lancet.
Amulti-research team from the UK, US and Canada warned that public healthmeasures that fail to treat the virus as predominantly airborne leave peopleunprotected and allow the virus to spread.
Silent(asymptomatic or presymptomatic) transmission of SARS-CoV-2 from people who arenot coughing or sneezing accounts for at least 40 per cent of all transmission.
Thissilent transmission is a key way Covid-19 has spread around the world,"supporting a predominantly airborne mode of transmission," as perthe assessment.
Bycontrast, the researchers found little to no evidence that the virus spreadseasily via large droplets, which fall quickly through the air and contaminatesurfaces.
"Theevidence supporting airborne transmission is overwhelming, and evidencesupporting large droplet transmission is almost non-existent," saidJose-Luis Jimenez, chemist at the Cooperative Institute for Research inEnvironmental Sciences (CIRES) and University of Colorado Boulder.
"Itis urgent that the World Health Organisation and other public health agenciesadapt their description of transmission to the scientific evidence so that thefocus of mitigation is put on reducing airborne transmission," Jimenezsaid.
Further,the researchers emphasise that while it is necessary to wash hand and cleansurfaces, they should be given less emphasis than airborne measures.
Ifan infectious virus is primarily airborne, someone can potentially be infectedwhen they inhale aerosols produced when an infected person exhales, speaks,shouts, sings, or sneezes.
Theairborne control measures include ventilation, air filtration, reducingcrowding and the amount of time people spend indoors, wearing masks wheneverindoors (even if not within 6 feet or 2 metres of others), attention to maskquality and fit, and higher-grade PPE for healthcare and other staff whenworking in contact with potentially infectious people.
Theteam reviewed published research and identified 10 lines of evidence to supportthe predominance of the airborne route.
Atthe top of their list: Super-spreader events such as the Skagit Choir outbreak,in which 53 people became infected from a single infected case. Studies haveconfirmed these events cannot be adequately explained by close contact ortouching shared surfaces or objects.
Moreover,transmission rates of SARS-CoV-2 are much higher indoors than outdoors, andtransmission is greatly reduced by indoor ventilation.
Theresearchers also cited work demonstrating long-range transmission of the virusbetween people in adjacent rooms in hotels; people who were never in eachother's presence.