University of São Paulo: Neglected in Brazil, ventilation reduced by more than 80% the risk of infection by covid in Italian schools

With the drop in mandatory masks, condemned by experts, there are fewer measures left to reduce the transmission of covid, but they do exist. One of them, quite effective and little applied in the Brazilian context, is the adequate ventilation of environments. A study conducted by the David Hume Foundation in the Marche region of Italy, compared data from more than 1,400 schools and concluded that the implementation of Controlled Mechanical Ventilation (MCV) systems in classrooms reduced the risk of infection by 82.5%. sars-cov-2 among students.

VMC is basically the use of exhaust fans to force the exchange of air, and was used in the context of the Northern Hemisphere, where the windows are sealed to maintain heating for most of the year. But the measure can be adapted to the context of Brazilian schools. Open windows and doors, and the placement of fans next to them, would already have the capacity to play the role of exhaust fans. However, more than a generic measure, the practice would have to be applied with quantitative measurement. Situations vary greatly in each school, and it is necessary to measure whether the action is already being able to make a good exchange of air, defends Erick Sousa, a researcher at the Covid-19 BR Observatory and a doctoral student at the Federal University of Goiás (UFG).

For this, it is necessary to use CO2 meters, relatively simple and inexpensive devices that are already widely used in some countries. There is even a federal law, prior to the pandemic (13,589/2018), with reference to the Anvisa resolution that addresses the importance of air renewal, citing monitoring with CO2 meters.

For environments that use air conditioning, such as companies, the exhaust system should be applied, and it would be a great reinforcement in preventing contagion. “But here in Brazil this issue was left aside, especially with the massive use of split -type equipment . If the air renewal was not included in the project, leaving it to be adapted later, it goes against the air conditioning, because the air placed outside in the environment warms the air-conditioned mass. And it ends up consuming more energy”, explains the researcher. Also for this reason, there is little interest from companies and establishments in applying the rule, and there is no inspection either.

“Careless and shallow”
For Lorena Barberia, professor at the Department of Political Science at the FFLCH and scientific coordinator of the Solidarity Research Network, an initiative of researchers aimed at improving the quality of public policies amid the Covid-19 crisis, the study by the Hume Foundation is very important. for doing an analysis isolating a specific factor and showing the wide variation in risk that changes in ventilation cause.

“Although we are dealing with a virus that is transmitted through the air, the public authorities’ treatment of this route of contagion is negligent and superficial”, points out the researcher. At the end of last year, the survey carried out by the Solidarity Network that prepared the Return to Classroom Safety Index showed that no State even mentioned ventilation and monitoring of CO2 in the air in its safety protocols.

And the issue still does not receive due attention in 2022, with the aggravating factor that other protection measures are being relaxed, as in the case of the elimination of the policy of reduced capacity in rooms. Lorena Barberia explains that protocols need to consider several complementary factors (vaccination, distancing, use of masks, ventilation and air quality) and that it is irresponsible to modify measures in one area without thinking about how to compensate for this in other areas. “Eliminating physical distancing without investing in CO2 monitoring or ventilation, for example, greatly exacerbates the risks,” she points out.

She also warns of the need to take climatic factors into account. There are several regions in Brazil where periods of extreme heat or cold make schools close their windows to heat the environment or turn on the air conditioning, and this tends to exacerbate the already alarming problems of lack of ventilation.

The study
The survey monitored cases of contagion attributable to infections that occurred within the classroom between September 2021 and January 2022. A total of 10,441 were observed, 56 of which were carried out in environments with some type of VMC system installed and active. The study report has not yet been published, but the USP Journal has had access to its results.

The researchers separated the systems into three categories, according to their efficiency range: those with an average number of air changes/hour of 2.4, those with an average of 4 air changes/hour and those with 6 air changes/hour. hour. In rooms with systems of the first category, the number of attributable cases was 40% than in rooms without any VMC. In the second, 66.8% lower. And in the third category, with the most efficient ventilation, it was 82.5% lower.

“What the research gave us was a quantitative, and statistically relevant, dimension of the real impact of ventilation. The study was able to compare the incidence of infections in schools with and without the exhaust system, including periods of high virus circulation in a region”, says Sousa, who did not participate in this work, but studies the topic and is part of an international network. of researchers focused on ventilation, Aireamos (“ventilamos”, in Spanish).

According to the authors of the study, the use of maximum efficiency VMC systems in schools could decrease the incidence rate of covid by up to five times, from 250 cases per 100,000 students to 50 cases per 100,000 students.

Safety index of return to face-to-face classes in Brazilian capitals in 2022

Reinforcement of vaccination
The robust influence of ventilation quality on Covid transmission rates in closed spaces is reinforced by other research. A study published in November 2021 in the scientific journal BMC Infectious Diseases sought to assess in which scenarios it would be safe to allow normal pre-pandemic crowding indoors. To do this, the researchers mathematically modeled several different combinations of site ventilation levels and number of subjects.

The results showed that, among the scenarios considered by them (a restaurant, a prison and a classroom), the classroom with an efficiency VMC of 6 air changes per hour (the maximum effectiveness among those analyzed by the Italian study ) was the one that had the lowest limit of immunized people necessary to control the transmission of the disease.
For schools, the difference in the minimum limit of people vaccinated for the natural ventilation scenario and for the scenario with high-efficacy CMV was more than 50%, which shows how important ventilation is within the scope of prevention measures.

“Focusing on the quality of ventilation in parallel with vaccination is especially important, considering the greater transmissibility of the delta variant and that vaccines do not offer 100% protection”, say the authors of the article, in addition to reinforcing that avoiding agglomerations remains a strategy of prevention. critical prevention.

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