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In recent weeks, the incidence of\u00a0COVID-19<\/a>\u00a0in Spain\u00a0has increased\u00a0.\u00a0In addition, recent scientific evidence shows that\u00a0minors seem to be infected between a third and a half than adults<\/a>\u00a0and that\u00a0if they are older than 10 years, they are just as contagious as adults<\/a>\u00a0.\u00a0Given this situation, the concern of families and teachers about planning to return to classrooms in the safest possible way has increased.<\/p>\n The issue affects all educational stages, from early childhood education to university.\u00a0In the case of universities, their representative bodies, in many cases, approved plans during the month of July based mainly on occupational safety protocols for their\u00a0workers<\/a>\u00a0.<\/p>\n To return to classrooms safely, the main thing is that the incidence of the disease is\u00a0low<\/a>\u00a0(for example, less than 25 cases per 100,000 inhabitants in the last 14 days).<\/p>\n Currently, all the autonomous communities far exceed these incidence values.\u00a0Despite this, the authorities have decided to start the course and have agreed on\u00a0unified measures for the entire territory<\/a>\u00a0.<\/p>\n Among them are some necessary ones, based on scientific evidence, such as the\u00a0mandatory use of a mask<\/a>\u00a0even if a distance\u00a0greater than 1.5 m is maintained<\/a>\u00a0for all students over 6 years of age and for teachers – with more reason, because they\u00a0will speak more frequently<\/a>\u00a0-.\u00a0It is also recommended to wash your hands on a regular basis and ventilate the classrooms on a frequent basis.\u00a0In addition, it is encouraged to take classes with the windows open.<\/p>\n However, it will also be mandatory to measure body temperature for students and teachers.\u00a0This measure has been shown to be\u00a0of doubtful efficacy<\/a>\u00a0, since a significant percentage of those infected, especially if they are minors, may not show fever and, in general,\u00a0the disease is much milder<\/a>\u00a0.<\/p>\n In addition, some autonomous communities (Galicia, Catalonia and Andalusia, for example) propose to carry out PCR tests, despite the fact that the test may be negative because, for example,\u00a0the viral load is low if the infection is recent<\/a>\u00a0.<\/p>\n Finally, it is also recommended to reduce the ratios per classroom, the blendedness and follow the isolation protocols once a case is detected.<\/p>\n The latest\u00a0scientific <\/a>evidence<\/a>\u00a0shows that in addition to being transmitted by drops or fomites (by contact with surfaces where there is an active virus), the virus\u00a0can be transmitted<\/a>\u00a0by aerosols.<\/p>\n More than\u00a0200 experts asked<\/a>\u00a0the WHO to include aerosols among the main modes of transmission of COVID-19.\u00a0The\u00a0institution<\/a>\u00a0listed the new route of transmission as secondary, even though it appears to be relevant in a\u00a0healthcare setting<\/a>\u00a0or isolated, such as a\u00a0cruise ship<\/a>\u00a0.<\/p>\n Despite the fact that the possibilities of contagion in the courtyard, dining room, changing rooms or school entrance should not be neglected, students spend most of their time in classrooms.\u00a0That is why it is very important to prevent these from becoming high-risk areas.<\/p>\n Transmission by aerosols can be of little relevance in open spaces, unless the safety distance is not respected or there is physical contact.\u00a0However, in closed spaces such as the classroom, even if the\u00a0safety distance<\/a>\u00a0is respected\u00a0, this route can represent an important part of the transmission of the disease if the space is not well\u00a0ventilated<\/a>\u00a0or the use of masks is limited.<\/p>\n In short, in addition to the mandatory use of masks and the need for them to be\u00a0well adjusted<\/a>\u00a0, the\u00a0quality of the air and ventilation<\/a>\u00a0, the\u00a0duration of classes<\/a>\u00a0and a low number of students per classroom, not only to reduce transmission but also to facilitate traceability, they have to be factors to take into account when scheduling the next course.<\/p>\n Everyone should wear a mask inside colleges and universities.\u00a0But how can we lower the concentration of the virus in the air in case someone is infected?<\/p>\n A possible solution to reduce transmission would be to give as many classes as possible outdoors.\u00a0With a mask, distance and relative silence, outdoors not only airborne transmission would be reduced, but also through contact with surfaces, since solar radiation reduces the time that the virus is active on a\u00a0surface<\/a>\u00a0.<\/p>\n In New York, outdoor teaching was already chosen during successive\u00a0tuberculosis<\/a>\u00a0pandemics\u00a0at the beginning of the 20th century and it\u00a0is being promoted<\/a>\u00a0from the mayor’s office for the next academic year.\u00a0By the way, there are very few areas in Spain where the average temperature in autumn and winter is lower than in New York, so the cold should not be an impediment.\u00a0In this sense, recently several city councils, such as\u00a0Barcelona<\/a>\u00a0, have offered those responsible for regional Education facilities and parks.<\/p>\n If\u00a0teaching\u00a0abroad is not feasible, different experts have created a\u00a0spreadsheet<\/a>\u00a0to estimate the probability of transmission of COVID-19 by aerosols based on the local incidence of the epidemic, the number of infected people, the size of the classroom, occupation, duration of class, percentage of people with a mask and type of mask, temperature, humidity (\u00a0the virus remains active less time for low relative humidity<\/a>\u00a0) and ventilation and air purification, among others variables.<\/p>\n Regarding ventilation and air purification, we must remember that knowing said quality is not only important as an indicator of virus concentration, but also influences the concentration of\u00a0students<\/a>\u00a0and\u00a0teachers<\/a>\u00a0.<\/p>\n To estimate air quality, we can\u00a0measure CO medir concentration<\/a>\u00a0in a simple and relatively inexpensive way.\u00a0In fact, the\u00a0Belgian Government will facilitate the acquisition of CO\u2082 meters<\/a>\u00a0for all classrooms in the country.\u00a0CO\u2082 concentration values \u200b\u200bshould be below 800 ppm.\u00a0From the CO\u2082 concentration we can\u00a0calculate<\/a>\u00a0the ventilation of the space.<\/p>\n Obviously, the first option is to use\u00a0natural ventilation<\/a>\u00a0to reduce the virus concentration.\u00a0It is highly recommended to have the windows open, as\u00a0Belgium is<\/a>\u00a0going to impose\u00a0for the next course.<\/p>\n The ventilation rates of the different teaching spaces range from 0.1-8 ACH (\u00a0air changes per hour<\/em>\u00a0) for a\u00a0primary school<\/a>\u00a0to between 2 and 12 ACH for a\u00a0university classroom<\/a>\u00a0.\u00a0The ACH variable expresses the fraction of initial air that remains in the classroom, a value of 1 means that after one hour 36% of the initial air remains.<\/p>\n If natural ventilation is not sufficient to improve air quality, which is the case in many older buildings, forced ventilation is necessary.\u00a0Outside air should be used and not recirculated, since the latter seems to be the reason for some of the lights in\u00a0restaurants<\/a>\u00a0.\u00a0In addition, ventilation devices should have filters installed, at least of the\u00a0MERV-13<\/a>\u00a0type\u00a0.<\/p>\n Finally, if the classroom cannot be naturally or mechanically ventilated, it is advisable to install\u00a0HEPA<\/a>\u00a0air purifiers\u00a0to minimize the risk of transmission, even though they are expensive.<\/p>\n In short, following what is indicated in this\u00a0guide from the Harvard School of Public Health<\/a>\u00a0to ensure the ventilation of classrooms, the ideal is to improve ventilation systems, incorporate air purifiers (or, at least, humidifiers), perform maximum outdoor activities and open doors and windows to achieve at least 5 ACH (air changes per hour) in 100 m\u00b2 classrooms occupied by 25 students.<\/p>\n The foregoing does not exclude the mandatory use of masks, hand hygiene, regular cleaning of surfaces and material, and maintaining a safety distance to minimize the transmission of SARS-CoV-2.<\/p>\nThe measures set by the communities<\/strong><\/h4>\n
The aerosol problem<\/strong><\/h4>\n
Outdoor classes?<\/strong><\/h4>\n
Measuring air quality in classrooms<\/strong><\/h4>\n
How to improve ventilation<\/strong><\/h4>\n