At a time when a mask has become a political statement, at least in the US, it is not surprising that the semantics between a drop (a small drop of liquid, just to clarify) and a spray (a suspension of solid particles matter of droplets of liquid in gas or, in this case, just air) should become a topic of much debate.
Which could explain the enthusiasm with which Friday’s update was received from the US Centers for Disease Control and Prevention on its website on “how Covid-19 spreads most often.” And which might explain why, less than 15 hours after it was widely reported (early Monday morning India time), the update was pulled, and the CDC claimed it was a draft that was published in error. .
“Through respiratory droplets or small particles, such as aerosols, that are produced when an infected person coughs, sneezes, sings, speaks or breathes. These particles can be inhaled through the nose, mouth, airways, and lungs and cause an infection. This is believed to be the main way the virus spreads, ”said the now-rescinded update. “There is growing evidence that airborne droplets and particles can remain suspended in the air and be inhaled by others, and travel distances beyond six feet (for example, during choir practice, in restaurants, or in fitness classes). In general, indoor environments without good ventilation increase this risk, ”he added. The language was very different from the CDC’s previous update (in June) on how Covid-19 spreads; That June update, now back on the organization’s website, said nothing about aerosols.
Because some may be overlooked, let me point out the “distances beyond six feet” in the rescinded update. I have seen people in conference rooms take off their masks quoting the six foot rule and continue speaking (out loud). Both, the upgrade that was not suggested, are risky. So is the 15-minute exposure threshold suggested by the CDC in a note from late July. I know of organizations that keep meetings under 15 minutes simply because of that: The Internet is a wonderful thing, but as the poet Alexander Pope said, “a little learning is one thing; drink deep, or don’t try Pieria’s spring. ”
The new CDC guidelines, which did not clearly point to the increased risk of transmission indoors, especially in shared rooms, but also in open offices with poor air conditioning and poor ventilation. And speaking (especially out loud, which is a natural reaction in conference rooms because everyone is spread out) was an added risk. Until now, it has been assumed that it is okay to speak without masks in socially distant gatherings (usually held in a closed room). Not so, the CDC update said. According to this, even the legislators separated by Plexiglas in the current session of the Indian Parliament are not sure. Most of those who speak do so without masks, which allows the circulation of aerosols (the plexiglass-glass is in front and to the side, not above).
The World Health Organization has been pestered for months by scientists who have asked to change their own advice on transmission to include the warning on airborne transmission. That has not happened. While it’s unclear what caused the CDC to change its mind, its rescinded update may still form the basis of guidelines that governments around the world can now write, to ensure the safe reopening of public spaces and the restart of public spaces. activities. There is enough evidence (based on research) to prove transmission of the virus by air.
These guidelines should cover two aspects: the physical and the behavioral. The first covers aspects such as the nature of ventilation and air conditioning, the number of people present and the distance between them, and the presence or absence of barriers (such as Plexiglas partitions). The second has to do with whether or not people wear masks, the amount of conversation (or shouting or singing), the length of the meeting or gathering, and the nature of the activity that people participate in (for example, a gym , where many people exercise and consequently gasp, is definitely more risky than a quiet ride on the subway).
This may seem like a lot of detail, but with a vaccine unlikely to be available until mid-2021, and life (and work) must go on, everyone has to learn to live with the virus, and that involves rules. , a lot of them, but all based on data and science, even if politics sometimes gets in the way.
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