Ten reasons why the coronavirus is in the air

There is steady, strong evidence that the SARS-CoV-2 virus, which causes COVID-19, is mainly transmitted through the air, according to a new review published in the medical journal today. Lancet. Therefore, social health measures that fail to treat the virus primarily in the air leave people unprotected and allow the virus to spread, according to six experts from the United Kingdom, the United States and Canada, including Jose-Luis Jimenez, a chemist at the Cooperative Institute for Research in Environmental Sciences (CIRES) and the University of Colorado Boulder.

“The evidence supporting air transmission is overwhelming, and evidence supporting large droplet transmission is almost non-existent,” Jimenez said. “There is an urgent need for the World Health Organization and other public health bodies to adapt their description of the transmission to the scientific evidence so that the focus on reducing the transmission is put in the air.”

The team of experts, led by Trish Greenhalgh, University of Oxford, reviewed published research and identified ten lines of evidence to support the dominance of the air route.

At the top of their list: Super-distributor events like the Skagit chorus outbreak, in which 53 people became infected from a single infected case. Studies have confirmed that these events cannot be adequately explained by close contact or touching shared surfaces or objects.

In addition, the transmission speed of SARS-CoV-2 indoors is much higher than outdoors, and the transmission is significantly reduced by indoor ventilation.

The team highlighted research that estimates that silent (asymptomatic or presymptomatic) transmission of SARS-CoV-2 from people who do not cough or sneeze accounts for at least 40 percent of all transmission. This silent transmission is an important way in which COVID-19 has spread around the world, ‘according to the assessment’. The researchers also cited work showing the long-distance transmission of the virus between people in adjoining rooms in hotels; people who were never in each other’s presence.

In contrast, the team found little or no evidence that the virus spreads easily through large droplets that quickly fall through the air and contaminate surfaces.

“We were able to identify and interpret highly complex and specialist articles on the dynamics of fluid flow and the isolation of live viruses,” said lead author Greenhalgh. “Although some individual articles were considered weak, the evidence base for air shipment is generally extensive and robust. There should be no further delay in implementing measures around the world to protect it.”

The new work has serious consequences for social health measures aimed at mitigating the pandemic. First, ‘drip measures’ such as hand washing and surface cleaning, although not insignificant, should be given less emphasis than air measures, which deal with the inhalation of infectious particles hanging in the air.

If an infectious virus is primarily in the air, someone may become infected when they inhale aerosols when an infected person exhales, speaks, shouts, sings or sneezes. The air control measures therefore include ventilation, air filtration, reducing the pressure and the amount of time people spend indoors, wearing masks when they are indoors (even if it is not less than 2 meters from others), attention to mask quality and fit, and higher degree Personal protection for health care and other staff when in contact with people who may be contagious.

“It’s surprising that someone is still questioning whether airborne transmission is the predominant transmission route for this virus or not,” said co-author Professor Kimberly Prather, a University of California aerosol scientist. “Only by inhaling aerosols at short and long distances can we explain the many indoor outbreaks that have occurred worldwide. Once we recognize that this virus is in the air, we know how to fix it. There is “There are many examples of places that are faring much better by acknowledging that this virus is in the air from the beginning. The world needs to follow their lead as soon as possible.”

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Professor David Fisman, a physician-epidemiologist at the University of Toronto: “It is critical for healthcare professionals to work with aerosol scientists and engineers. Establishing aerosol transfer as the dominant mode of transmission of SARS “Is actually good news, because we have a wealth of expertise to reduce the risk of aerosols. But these tools will not be used as long as public health agencies are not clear on how this disease spreads.”

Dr. Robert Schooley of Infectious Diseases, Professor at the University of California, San Diego: ‘If one starts with the understanding that the virus repeats in the lungs and is exhaled with each breath in a range of particle sizes, some of which are far beyond the magic area can move 6-foot curtain is considered the limit for drops – and can persist in poorly ventilated areas – it is inevitable to conclude that public health strategies should focus on those that reduce the spread of respiratory pathogens in the air . “

Professor Zeynep Tufekci, a sociologist at the University of North Carolina, Chapel Hill, said: ‘It is essential that the guidelines for the public accurately explain the transmission mechanisms and their relative importance, rather than focusing on binary rules such as ‘six feet’ that do not apply the even after a whole year, we still see the widespread practice of unnecessary cleaning levels to the detriment of public health, the use of plexiglass indoors that is far from adequate protection, and depending on airflow, even contraindicated, instead of paying attention to ventilation and aerosol risks. We cannot rectify this situation without accurately informing the public so that people feel empowered to make decisions to better protect themselves across different contexts, and to adapt guidelines worldwide to match the best available evidence. ‘