Is the air that we breathe, no longer safe? Renowned virologist Dr T Jacob John breaks down CDC’s most recently updated Covid-19 guidelines, and what they mean for India
Local train services were opened to the public in February this year. Were authorities warned about the four to five variants that had the potential to spread fast, they would not have taken such risks, feels Dr John. Pic/Satej Shinde
Last Friday, almost a year into the pandemic, the US Centers for Disease Control (CDC) finally changed its guidance to acknowledge that SARS-CoV-2, the virus that causes Covid-19, can be transmitted through air. This new language is a significant change from the agency’s previous position, which stated that the virus only spread through “close contact” and was not airborne.
In the past, scientists and epidemiologists have repeatedly warned about the need for greater acknowledgement of the role of the airborne spread of Covid-19, in order to help governments to implement more effective control measures.
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In July 2020, nearly 239 scientists from 32 countries in an open letter, published in the journal Clinical Infectious Diseases, had even highlighted that the threat of the virus lingering in the air was being underplayed by the World Health Organisation (WHO).
Dr T Jacob John
For India, which is currently battling the second wave and is the worst-hit country in the world, having this knowledge beforehand, could have stemmed the spread of the infection significantly, says Dr T Jacob John, leading virologist and former professor at the Christian Medical College, Vellore. “What is new is not merely our understanding [of the way transmission occurs], but mainly the biology of the virus,” he says.
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Edited excerpts from the interview:
How important is this development—the virus being an airborne threat—for the scientific and research community in understanding it?
I would not use the categorical statement of “airborne threat” for Covid-19. In fact, there is very little new in the CDC Guidelines of May 7, 2021. If A is infected and B stands at three or five feet and gets infected, the medium between them is air alone, so the infection was always transmitted “through” air. The usual limit [of safe distance] is said to be six feet, or two metres.
If the two are separated by eight feet, but the two stay where they are for more than say 15 minutes, then, the probability of some virus particles in the air inhaled by B increases from zero to a small degree. Now, the distance and time dimensions come into play.
If they are in closed doors without ventilation, and if there were more people, and among them, there were more than one infected persons, then some virus can float in the air and infect persons even at distances of more than eight feet.
The third factor is virus concentration in the air—more viruses being added to the air that is not getting exchanged from outside since the hall is not well ventilated. Here, chances of infection in uninfected people increases. In the above two examples, the virus is “airborne”.
The new variant matters too. Even if one person in the room was integrated, and s/he expels large amounts of virus —because of high virus load, which is the case with the new B.1.617 variant, then airborne transmission is more likely now than it was for the earlier D614G variant.
Would you say that this new understanding of the way the transmission occurs would also drastically change the way we fight or prevent the infection?
This new information will definitely help us modify our preventive behaviour and interventions. First of all, mask-wearing is our best preventive measure; one hundred per cent people must wear masks. What happened to the discipline of masks? Who destroyed that behaviour that was picking up nicely in India? Whoever was responsible to teach people by words and deeds that masks were not important, is guilty of contributing to the second wave. Remember, vaccines will protect against disease, but masks will protect you against getting the infection in the first place. Masks slow down the spread of infection. The second wave was helped by political leaders, who trivialised the value of masks.
Next, crowding: the airborne risk of transmission is to be mitigated by disallowing crowds, particularly with variants and air-borne transmission becoming a reality. Whoever flouted that principle on large scale, whoever failed to provide data and advice, whoever took huge risks for huge populations (are) collectively guilty of “unintentional mass homicide” by “public health negligence” (like medical negligence for individuals).
The new information, researchers have shared, could have significant implications for indoor environments, and workplaces in particular. Why is that so?
It’s physics. Pollutants—visible or smellable—or unseen viruses, stay longer in air in closed environments.
Do you feel that India’s devastating second wave could have been contained, if this information would have come to us earlier, especially with cities like Mumbai opening up its public transport earlier this year?
Yes, indeed. The change was heralded by a shift from the D614G variant that predominated the first wave during 2020, which was slowly getting replaced by faster-spreading variants in December 2020 and onwards into 2021. If INSACOG [Indian SARS-CoV-2 Genome Sequencing Consortia] virologists were required to analyse genomically 5 per cent of all RT-PCR positive specimens, from December 2020, epidemiologists would have been warned about the four to five variants that had the potential to spread fast in India and we would not have let our guard down as we did from January 2021. As we sow, so we reap.
Donald Milton, an aerosol scientist at the University of Maryland, in an interview to the New York Times, shared that we’d probably need better guidelines for keeping workplaces and other indoor environments safe, and also focus on good respirators (and not just masks) for people, like for bus drivers, “who have to be close to other people for long periods of time”. Your thoughts?
Where are the Indian scientists advising the government of India on such matters? Why not have all such people vaccinated on priority with two doses and their immunity checked and certified?
Do you think it’s the more infectious variant in India and the world that compelled the need to change the CDC guidance?
Yes. I use the word variants—more infectious variants, not strain. I feel the virus has remained as one strain so far.
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