Updated: July 15, 2020 10:24:39 am
The WHO has formally recognized the possibility that the new coronavirus may remain in the air in crowded indoor spaces, where “short-range aerosol transmission cannot be ruled out …”. (Express photo: Amit Chakravarty)
The World Health Organization (WHO) released on Thursday (July 9) an updated version of its scientific report of March 29, ‘Modes of transmission of the virus that causes COVID-19: implications for prevention precautionary recommendations and infection control (IPC) ‘, which said included “new scientific evidence available on the transmission of SARS-CoV-2, the virus that causes Covid-19”.
In summary, the WHO has formally recognized the possibility that the novel coronavirus may remain in the air in crowded indoor spaces, where “short-range aerosol transmission … cannot be ruled out.”
The updated report came three days after a group of 239 scientists from 32 countries published a comment titled “Time to Address COVID-19 Air Transmission,” in which it issued an “appeal to the medical community and relevant country. and international organizations to recognize the potential for the spread of COVID-19 in the air. “
Previously on Tuesday (July 7), a day after the scientists’ open letter was published, Maria van Kerkhove, WHO technical leader on the pandemic, had said at the Covid-19 daily press conference that ” We have been talking about the possibility of airborne and aerosol transmission as one of the modes of virus transmission. ”
So what has the WHO said in its updated report?
Referring to several recent studies, the WHO has said that some outbreaks that have occurred in crowded indoor spaces suggest “the possibility of transmission of aerosols”, although “combined with the transmission of drops.” Such situations have arisen “during the practice of the choir, in restaurants or in gym classes”.
According to the WHO, “in these events, transmission of short-range aerosols cannot be ruled out, particularly in specific indoor locations, such as crowded spaces and inadequate ventilation for an extended period of time with infected persons.”
However, there is a caveat: The WHO does not believe that, even in these situations, the virus was transmitted exclusively by air.
The WHO report still says that “detailed research from these groups suggests that the transmission of droplets and fomites may also explain person-to-person transmission within these groups.”
Transmission via respiratory droplets, when an infected person coughs, sneezes, speaks, or sings, is still understood as the primary mode of transmission of the virus.
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Fomite transmission, on the other hand, refers to transmission through infected surfaces, such as door knobs, elevator buttons, handrails, telephones, switches, pens, keyboards and, if not disinfected, even the stethoscope of a doctor.
But what is important is that the WHO has previously maintained that airborne transmission of the virus is not a concern outside of situations where healthcare workers participate in certain medical procedures that generate aerosols.
And although it still continues to emphasize that “current evidence suggests that SARS-CoV-2 transmission occurs mainly between people through direct, indirect or close contact with infected people through infected secretions such as saliva and respiratory secretions, or through their respiratory droplets, “The new report acknowledges that aerosol transmission can also occur” outside of medical facilities. “
However, the new report does not address the issue of the relative contributions of droplet, fomite, and aerosol transmission to the spread of Covid-19. There is not enough evidence yet, he suggests.
He says: “High-quality research is urgently needed to elucidate the relative importance of different transmission routes; the role of air transmission in the absence of aerosol generation procedures; the dose of virus required for transmission to occur; the configuration and risk factors for over-predation events; and the extent of asymptomatic and pre-symptomatic transmission. “
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But is the fact that aerosol transmission really can happen, as the 239 scientists who wrote the open letter underscored, and what the WHO has now recognized, a new revelation?
There has already been some evidence of aerosol transmission in the investigation.
* * One of the first studies, published in Nature, was conducted at Renmin Hospital and Wuchang Fangcang Field Hospital in Wuhan. He investigated the aerodynamic nature of the SARS-CoV-2 virus by measuring its viral RNA in aerosols.
This study found that the concentration of the virus in aerosols detected in isolation rooms and ventilated patient rooms was “very low”, but was “higher in the bathroom areas used by patients.”
“The SARS-CoV-2 RNA levels in the air in most public areas were undetectable, except in two areas prone to crowding,” the study said. “Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 can be transmitted through aerosols.”
* * In April, a correspondence published in NEJM by researchers from the US National Institute of Allergy and Infectious Diseases in the United States assessed the stability of SARS-CoV-2 (and SARS-CoV-1, which causes SARS). in aerosols and on various surfaces
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SARS-CoV-2 was found to “remain viable in aerosols” throughout the three-hour experiment. “Our results indicate that the transmission of SARS-CoV-2 by aerosol and fomite is plausible since the virus can remain viable and infectious in aerosols for hours,” the study said.
The WHO did not agree with these findings. “… The finding of the COVID-19 virus in aerosol particles of up to 3 hours does not reflect a clinical environment in which aerosol generation procedures are performed, that is, this was an experimentally induced aerosol generation procedure”, had said.
* * In May, the US Centers for Disease Control and Prevention (CDC) published a study titled “High SARS-CoV-2 Attack Rate After Exposure in Chorus Practice.” The researchers, who studied “super-grasp events,” found that after 2.5-hour choir practice, 61 people attended, including one symptomatic index patient, 32 confirmed secondary cases and 20 probable secondary Covid-19s occurred; three patients were hospitalized and two died.
The study noted that “the act of singing” itself could have contributed to “transmission through aerosol emission, which is affected by the volume of the vocalization.” “Certain people, known as super-emitters, who release more aerosol particles during speech than their peers, may have contributed to this and previously reported COVID-19 super-predation events,” she said.
“… The emission of aerosols during speech has been correlated with the volume of the vocalization, and certain people, who release an order of magnitude more particles than their peers, have been referred to as super transmitters and have hypothesized that they contribute to super speed events. Members had intense and prolonged exposure, singing while sitting 6 to 10 inches from each other, possibly emitting aerosols, “he said.
How is life changing for you and me now? What does the fact that air transmission is possible mean?
Basically it means that wearing a mask becomes even more important than before.
It could be possible that N-95 masks, which are worn by doctors in hospital settings, may now be recommended to prevent the transmission of aerosols, subject to availability and depending on a person’s state of health.
In its section on “How to prevent transmission,” the WHO report said that apart from handwashing and physical distancing, one should “avoid crowded places, places of close contact, and confined and closed spaces with poor ventilation” and “Wear cloth masks when you are indoors and overcrowded to protect others; and ensure good environmental ventilation in all closed environments and adequate environmental cleaning and disinfection.”
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