A quiet revolution has permeated global health circles. Authorities have come to accept what many researchers have argued for over a year: the coronavirus can spread through the air.
This new acceptance, by the World Health Organization and United States The Centers for Disease Control and Prevention have real-world implications: Scientists are calling for ventilation systems to be overhauled like public water supplies in the 1800s after foul pipes were discovered. cholera.
Cleaner indoor air will not only fight the pandemic, it will minimize the risk of catching the flu and other respiratory infections that cost the United States more than $ 50 billion a year, researchers said. in a study published Friday in the journal Science. Avoid these germs and their associates disease and productivity losses would therefore offset the cost of improving ventilation and filtration in buildings.
“We are used to the fact that we have clean water coming from our taps,” said Lidia Morawska, a distinguished professor in the School of Earth and Atmospheric Sciences at the Queensland University of Technology in Brisbane, Australia, who led the study. Likewise, “we should expect clean air free of pollutants and pathogens” from indoor spaces, she said of Zoom.
The study’s authors, comprising 39 scientists from 14 countries, are demanding universal recognition that infections can be prevented by improving indoor ventilation systems. They want the WHO to expand its indoor air quality guidelines to cover airborne pathogens, and for building ventilation standards to include airflow rates, filtration rates and airflow rates. higher disinfection, and monitors that allow the public to assess the quality of the air they breathe.
A ‘paradigm shift is needed at the scale that occurred when Chadwick’s health report in 1842 led the British government to encourage cities to organize centralized drinking water supplies and sewage systems, ”they wrote.
“No one takes responsibility for the air,” Morawska said. “It is sort of accepted that air can be of any quality – containing viruses and pathogens.”
SARS-CoV-2 multiplies in the airways, allowing it to spread into particles of different sizes emitted from the nose and throat of an infected person during breathing, speaking, singing, coughing and sneezing.
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The larger particles, including visible spattering sputum, fall quickly and settle on the ground or on nearby surfaces, while the tiniest – aerosols invisible to the naked eye – can be carried further and stay in the air longer, depending on humidity, temperature and air flow.
It is these aerosol particles, which can linger for hours and travel indoors, that have fueled the controversy.
Even if airborne infections, such as tuberculosis, measles and chickenpox are more difficult to trace than pathogens transmitted through contaminated food and water, research over the past 16 months supports the role aerosols play in the spread of the pandemic virus.
This has led to official recommendations for wearing public masks and other infection control strategies. But even these came after aerosol scientists pushed for tougher measures. minimize the risks.
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Morawska and a colleague published a an open letter backed by 239 scientists last July asking authorities to approve additional precautions, such as increasing ventilation and preventing the recirculation of potentially virus-laden air in buildings.
The WHO guidelines have been amended at least twice since, although the Geneva-based organization says the coronavirus spreads “primarily between people who are in close contact with each other, usually within 1 meter ”, or about 3 feet.
Morawska, who runs a WHO collaborating center on air quality and health, says this is an oversimplification.
“There is nothing magical about this 1 meter,” said Morawska. The closer an infected person is, the higher the concentration of infectious particles and the shorter the exposure time it takes for infection to occur. “The more you move away, the concentration decreases,” she says.
According to Morawska, infectious aerosols stay concentrated in the air longer in confined and poorly ventilated indoor spaces.
While a high density of people in such environments increases the number of people potentially exposed to airborne infection, closed indoor areas that are not overcrowded can also be dangerous – a distinction Morawska says the WHO should clarify.
“WHO, step by step, is changing the language,” she said.
Morawska, a Polish-born physicist who was previously a member of the The International Atomic Energy Agency can take credit for the change in WHO’s stance, said Raina MacIntyre, professor of global biosafety at the University of New South Wales in Sydney.
“Professor Morawska’s contribution, against a background of cutting-edge expertise in the field of aerosol science, has had a real impact in forcing the hand of the WHO,” MacIntyre said in an email.
‘Hygiene theater’The role of airborne transmission “has been denied for so long, in part because expert groups advising the government have not included engineers, aerosol scientists, occupational hygienists and multidisciplinary health experts. environmental, ”MacIntyre wrote in The conversation last week.
“A false narrative dominated public debate for over a year,” she said. “This resulted in theater of hygiene – rubbing hands and surfaces for little gain – as the pandemic wreaked massive destruction around the world.
Some people working in infection prevention and control and related fields have stuck with beliefs that aerosol transmission minimized, despite evidence challenging their point of view because “they don’t want to lose face. “, said Julian Tang, clinical virologist and Honorary Associate Professor in the Department of Respiratory Sciences at the University of England, Leicester.
“We all need to adapt and progress as new data becomes available,” Tang said. This is especially true in the area of public health, where official policies and guidance based on “outdated and unsubstantiated thinking and attitudes can cost lives,” he said.
Morawska said she hopes the attention the pandemic has drawn to face masks and the risks associated with inhaling someone else’s exhaled breath will be a catalyst for cleaner indoor air.
“If we don’t do the things we say now, the next time a pandemic strikes, especially a pandemic caused by a respiratory pathogen, it will be the same,” she said.