Against Covid, the (failed) air purification revolution

CORONAVIRUS – A highly contagious virus that is transmitted through the air we breathe, corpses taken by boat to hastily dug burial sites, a death toll of 16,000 in a single day at the peak of the epidemic… we are not in Paris during the Covid pandemic, but in Constantinople, in 542. Justinian’s plague, one of the first documented by historians, then deeply destabilizes the Byzantine Empire.

Yersinia pestis is not SARS-CoV-2, just as the understanding of diseases has nothing to do today with that which prevailed in late antiquity. But in addition to marking their time, these tragedies separated by 15 centuries have one thing in common: their main vector of contamination is airborne. A mode of transmission which, today perhaps even more than yesterday, continues to be underestimated, at a time when the fifth wave of coronavirus is finally retracting.

“The coronavirus is transmitted at 99% in poorly ventilated closed places”, thus summarizes the epidemiologist Antoine Flahault at HuffPost. This means, he adds, that “if we made indoor air as safe as the street, we would reduce contamination by 99% […] This is what we should focus on”.

Aerosol transmission, an (too) well-established fact

The airborne transmission of the virus was the occasion for notorious scrambles: we remember Sibeth N’Diaye understating the importance of masks, or even the hesitations of Jean-Michel Blanquer, the Minister of Education. In November 2020, he considered air purifiers dangerous, before changing his mind a few months later…by being wrong, they failed to attack the problem of transmissions from the start. Yet, clues were already there.

As early as April 2020, the Scientific Council highlighted in an opinion “the risk of aerosolization” of the coronavirus, a welcome intuition when studies on the transmission of the disease were still insufficient. You have to “air your home for ten minutes, three times a day”, advised Emmanuel Macron to the French a few months later, at the start of autumn.

Almost two years later, however, air purification is undoubtedly a poor relation of the prevention policy against Covid. Admittedly, ventilation is a barrier gesture. Admittedly, the circulars continue, like the health protocol of January 2022 for the professional environment, to encourage regular airing of the rooms. But no comprehensive policy is in place. Worse, the most basic reflex in this area, that of measuring the CO2 level of a room to find out if it is necessary to ventilate, has not caught on in the population.

Apathy as politics

On November 12, 2021, an investigation by the newspaperThe Parisian made a finding that hardly suffered from dispute, by going to measure the famous rate in various closed places open to the public. Supermarket, gymnasium, cinema, train: each time the account is not good. The only exceptions are the metro (where the outside air rushes in heavily), and the schools tested, where the teachers scrupulously opened the windows to let in the fresh air.

The school is an emblematic case of the apathy of public authorities on the question. Since 2021, the government has been in favor of installing air purifiers and CO2 detectors in classrooms. But no obligation, and especially no funding for the establishments: the machines remain the responsibility of the municipalities, which today still have not finished equipping themselves with them.

Faced with this policy in dribs and drabs, a group of doctors and teachers sounded the alarm in December 2021. “The government has still not taken full measure of prevention in schools in viral transmission by aerosol” accused the eighteen signatories of a column published in The world. A problem far from being confined to school, and far from being uniquely French.

The dress rehearsal for SARS

“We haven’t done enough, and we’re continuing,” exasperated epidemiologist Raymond Tellier when asked about the subject. It must be said that the Quebec researcher has good reason to be fussy on the subject. In January 2021, he participated in an appeal to the Canadian government, signed by 363 professionals, to realign its prevention policy towards aerosol contamination.

The open letter did not demand anything revolutionary, like the demands of the world of education in France: inspection of ventilation systems, distribution of HEPA air filters in poorly ventilated places, systematic installation of CO2 detectors. .. but again, the disappointment was there.

“The deployment of these measures is still dragging its feet”, estimates the specialist. “And what is even more frustrating is that we missed the boat at the start of the pandemic, when other respiratory diseases are caused largely by aerosol transmission”.

Starting with SARS, responsible for an epidemic that started in Southeast Asia in 2003. “I was a microbiologist in Toronto,” recalls Raymond Tellier. At the time, a peak of contamination takes place in the Canadian capital, which will result in 44 deaths in total. Contaminations then take place in the hospital. “It stopped when they introduced the mandatory wearing of N95 masks and measures against aerosol contamination.” A real laboratory, on a smaller scale, of what the specialists would have wanted in the face of SARS-CoV-2.

A short-term political problem…

Why this apathy in the fight against aerosol transmission, especially compared to efforts to disinfect surfaces, which have nevertheless demonstrated their ineffectiveness in the face of Covid? To answer this question, we must distinguish between the fight against the current pandemic and long-term health policy.

There is indeed an aspect of political communication on which researchers agree. “Politicians do not want to appear to be twirling according to studies”, thus analyzes Antoine Flahault, but “many scientists have been in favor of cleaning surfaces”. It would therefore look like a step back from the public authorities. And communication is not as simple as on other topics.

Purifying indoor air, “it’s not as sexy as an RNA vaccine” summarizes the epidemiologist. Especially since if, in principle, the importance of air renewal is well understood, its implementation can be a technical headache. Air circulation, especially in old buildings, has not been designed for rapid renewal. Sometimes it’s even the other way around.

…and a long-term health problem

Until the 19th century, explains Raymond Tellier, “buildings were even specifically built to prevent outside air from entering”. At the time, the dominant health theory was still that of miasma: it was considered that the air in the street carried disease. Since then, things have changed, for the better… but also, for the worse.

The reaction against the miasma theory, “at the start, it is justified” outbids Raymond Tellier, however. The 20th century establishes that in contagious diseases, the source of infection is not the air, it is the patient who is infected. We then move on to a new theory: that of surface hygiene.

A modern theory justified by many epidemics: Ebola, for example, is widely transmitted by direct contact with contaminated corpses. But Covid-19 is transmitted by aerosol. Surface hygiene is no longer enough. “The problem is that we completely deny the possibility of an infection transmitted by air which would emanate from the patient”, explains Raymond Tellier.

In other words, surface hygiene would have thrown the baby out with the bathwater. For about fifty years, however, aerosols have made a forced comeback in the understanding of epidemics: in 1960-1962, research on tuberculosis showed that the disease was mainly spread by air. A door nevertheless barely ajar in the health doxa.

Since then, all studies have had to “fight against the dominant dogma”, analyzes Raymond Tellier, “which was that aerosol transmission is something very, very rare, and that most diseases are transmitted either by contact directly, or by a third party [une surface infectée, par exemple]”. Measles, smallpox, flu…up to SARS-CoV-2. But this time, many epidemiologists are calling for a small health revolution.

“Paradigm Shift”

This is the case of Lidia Morawska, physicist and specialist in atmospheric air quality at the University of Queensland, Australia. It also advises the World Health Organization on all air quality issues. The researcher is one of the first to have used an expression that comes up in the mouths of many scientists: the coronavirus is an opportunity to “change the paradigm”.

The phrase is at the top of the study published in the journal Science in May 2021, of which Lidia Morawska is one of the main authors. In this concise text, the researchers recommend a health policy that finally recognizes the importance of aerosol contamination. “The COVID-19 pandemic has shown how unprepared we were for it, despite the knowledge gained during previous pandemics,” the article concludes. “We need to lay the foundations for the air in our buildings to be clean”.

And that requires a real revolution, like the health revolution that took place in the 19th century with drinking water. “It’s the next cycle in infection control,” argues Raymond Tellier. He too is calling for a paradigm shift, “in the same way we took care of water to avoid microbial contamination”.

Filter diseases…and pollution?

This development, emanating from the scientific community to spread not only to decision-makers but to public opinion in general, must manifest itself in a change in our relationship to the air we breathe. But beware, this does not mean a return to the miasma theory of the 19th century. This is to clean up the indoor air, as for the 19th century, it was the open air that was believed to be stale.

By rethinking the ventilation of buildings to ensure that they are not carriers of pathogens, we would do the equivalent for public health of the establishment of sewer networks in cities, assure the promoters of this transition to a “superior sanitary stage” as Raymond Tellier defines it. Not only could pathogens like the coronavirus be excluded from indoor space, but it could also help fight the effects of pollution, especially fine particles.

Without forgetting the need to tackle the ecological problem at the source, cleaning up our indoor air could also be a new step for public health. “In the 19th century”, recalls Raymond Tellier, “it was not only diseases, but also waste water that was poured into the rivers”.

See also on The HuffPost: Covid at School: Blanquer Announces New Lightened Back-to-School Protocol

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