We face New Year's Eve and Kings with the most contagious human transmission virus in history, the omicron variant of SARS-CoV-2. With this high incidence, social interaction with non-partners is equivalent to going through a minefield, especially indoors. On the International Day of Preparedness for Epidemics, this December 27, We collect advice from scientists to avoid contagion in these holidays, with special emphasis on air quality and masks, perhaps the great pending subjects for the improvement of the prevention.
Jose Luis Jimenez, Professor of Chemistry at the University of Colorado, recalls that we become infected by breathing infected air (aerosols with viruses) exhaled by some (not all) of the infected, in close proximity and in shared air in the room. It is 20 times more likely to be infected indoors than outdoors.
Distance and time
Indoors, distance helps, but it's not enough. This virus is transmitted mainly by aerosols, more concentrated in the proximity of the emitter, and that in poorly ventilated places float for hours, like tobacco smoke. Try to minimize time indoors, with as few people as possible. "The greater the number of people with whom we meet, the more chances there are that some of them may be asymptomatic and transmit the infection to us," he recalls Juan J. Gestal, epidemiologist and emeritus professor at the University of Santiago.
Lower your voice
Vocalization (speaking, shouting, singing) is strongly associated with transmission: as José Luis Jiménez recalls, many outbreaks have been verified in choirs, but none in libraries. Try to speak softly or not speak when possible, for example in public transport. And it's impossible with loud music at parties.
Masks are not sieves and must fit snugly
Masks, the most effective measure indoors to avoid contagion, are not strainers or sieves: thanks to microscopic physics they filter aerosols much smaller than the tiny holes they have between their fibers. They must be well adjusted and do not leave gaps: a space of only 2% of the mask surface allows 50% of the aerosols to pass.
FFP2 or FFP3, now more than ever
Germany and Italy have already established the obligation to wear FFP2 or FFP3 masks indoors, which are more effective. A study published in December by the Max Planck Institute in Germany found that well-fitting FFP2 masks reduce the risk of infection with COVID-19 0.1%. They are more necessary than ever due to the greater contagion of the delta and omicron variants, now the majority. On December 9, the Government announced the extension of the reduced VAT for hygienic and surgical masks, but left out the FFP2 and FFP3, to which a 21% tax is still applied. The Circle of the Health, chaired by the Galician Ángel Puente, has asked for the tax on these masks to be reduced, which have proven to be "more effective in protecting against contagion."
Measuring CO2 prevents opening windows wide in winter
Ventilation is crucial indoors. It must be continuous, crossed, distributed and measured. It is advisable to open windows on opposite sides of the room, but - especially in winter, with windy weather - it may be enough to leave openings. To find out we can use a CO2 meter with an infrared sensor (NDIR), which costs around 100 euros. The CO2 level should not exceed 700 to 800 parts per million.
CO2 measurement in hospitality, much improvement
Not a few restaurants and bars use electrochemical sensor devices that offer unrealistic readings. Nor do they always place them in visible places to customers or ventilate when CO2 levels exceed recommended thresholds. Jiménez and the scientists of the Aireamos platform urge to install CO2 meters visible to the public in all places where we share indoor air. It can be done for about 200 euros per location, a ridiculous investment if we consider the losses due to the pandemic and that will not only serve to combat COVID-19, but also other diseases, and even improve the cognitive level of those who occupy the room.
Filtering the air helps
If the ventilation is not enough or is not practical, the air can be filtered. José Luis Jiménez points out that commercial HEPA (high-efficiency) filters "work well, but are expensive.". There is a great variety according to cost, quality, and noise. Inexpensive fan filters work very well and you can make them yourself for about $ 40. They are called Corsi-Rosenthal boxes and there are videos on YouTube that explain how to assemble them.
No measure is perfect
You have to be aware that there are no "magic bullets", no measure is perfect to stop contagion. "In the interior there is no measure that by itself keeps us safe, we must do several things to reduce the risk", emphasizes Jiménez. We must adopt the "Swiss cheese" model proposed by the virologist Ian McKay, in which all the layers protect but have holes: vaccines, masks, ventilation, interpersonal distance, hand hygiene, testing through antigen tests, cleaning the air ... Unity is strength.
Two examples of what is done wrong
The upper image corresponds to the traditional Christmas Concert of the RTVE Orchestra and Choir, held last Friday in the Chapel of the Royal Palace of Madrid. Mesh masks do not work, as experts have repeated a thousand times. The lower image was taken by the Galician filmmaker Rodrigo Cortes on the AVE Seville-Madrid. As he denounced on Twitter, that level of CO2 is unhealthy.