Amid continuing scientific debate worldwide over whether airborne transmission of Covid-19 is possible, the Council of Scientific and Industrial Research (CSIR) has started air sampling studies to draw its own conclusions. Director general Dr Shekhar Mande has stressed that this is a sensitive public health issue and the CSIR does not want to falsely alert the public.
What do we know about airborne transmission?
While the virus that causes Covid-19, SARS-CoV-2, does spread through respiratory droplets from one person to another, it has remained up for debate whether droplets, including tiny aerosols, containing the virus remain suspended in the air for a long enough period of time to enable the virus to infect a new person.
Amid the debate, the World Health Organization (WHO) has updated its guidelines. While WHO had already acknowledged that airborne transmission can occur during medical procedures that generate aerosols, the updated guidelines state that “WHO, together with the scientific community, has been actively discussing and evaluating whether SARS-CoV-2 may also spread through aerosols in the absence of aerosol generating procedures, particularly in indoor settings with poor ventilation”.
The US Centers for Disease Control and Prevention (CDC), too, had issued a statement that the virus could spread through airborne particles that can remain suspended in the air and travel beyond 6 feet, but removed it recently saying it was updating the recommendations.
CSIR’s Dr Mande told The Indian Express: “Neither CDC nor CSIR will go to the public announcing whether it can be airborne or not. See, this is a sensitive public health issue and we do not want to falsely alert the public or falsely make them secure, and hence we are very cautious in our approach. But our air sampling studies have taken off.”
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What will the CSIR study look at?
The aim is to collect air samples from intensive care units, hospital corridors, waiting rooms and places where healthcare workers are most at risk and then investigate and understand whether airborne transmission is a possible route contributing to the pandemic.
“We cannot say confirmatively but we do see a situation where the virus is likely to be detected from the air. Now we have to figure out how far this virus can travel and in what amounts so that we can rule out several concerns,” said Dr Rakesh Mishra, Director, CSIR–Centre for Cellular and Molecular Biology.
CSIR–CCMB is in talks with hospitals across Hyderabad to involve them in the study. At CSIR–Institute of Microbial Technology, Chandigarh, Director Dr Sanjeev Khosla said they were in talks with the Punjab government to involve ICUs, swab collection centres and quarantine centres in the study.
What is the methodology?
Both institutes have got air samplers — handheld machines in which the air passes through a filter so that virus particles get stuck on it. These filters are then analysed to estimate for virus quantity. Several filters will be required as each has to be replaced while collecting new samples.
Dr Khosla said researchers will have to collect air samples a few hours after a Covid-positive patient leaves a particular room. Samples will have to be collected multiple times with different patients at distances of 4 ft, 8 ft and 12 ft.
“We need hundreds of data points and only then can arrive at some conclusion,” Dr Mishra said.
Why was this felt necessary?
“People are still worried about going to public places. There have been contrary studies on the airborne transmission and we wanted to check for ourselves just how the aerosols could travel and where the highest concentration of virus is likely to be present,” Dr Khosla said.
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A droplet is a liquid secretion coming out of the nose/mouth and is a heavy large particle that travels a short distance, while an aerosol is a lighter particle that travels longer, explained Dr Sundeep Salvi, Director, Pulmocare Research and Education (PURE) Foundation. “More studies are required to understand the possibility of aerosol route of transmission as it could have larger economic and social implications,” Dr Salvi said.
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