BENGALURU: In an interesting study, IISc researchers have found that the risk of getting infected with SARS-CoV-2 was higher when one person acted as a passive listener and didn’t engage in a two-way conversation. They also showed that factors like height difference between the people talking and the quantity of aerosol released from their mouths also plays an important role in viral transmission. Interestingly, they found that the risk of infection was low with moderate height.
The team of researchers is from the Department of Aerospace Engineering, IISc, along with collaborators from the Nordic Institute for Theoretical Physics (NORDITA) in Stockholm and the International Centre for Theoretical Sciences (ICTS) in Bengaluru. Their study was published in the journal Flow. They used new computer simulations on how speech droplets or aerosols move in the air space between interacting people.
According to a release by IISc, the team visualised scenarios in which two maskless people are standing two, four or six feet apart, and talking to each other for about a minute, and then estimated the rate and extent of spread of the speech aerosols from one to another. Their simulations showed that the risk of getting infected was higher when one person only listened and didn’t participate in the conversation.
Sourabh Diwan, Assistant Professor in the Department of Aerospace Engineering, and one of the corresponding authors, explains that “very few studies have looked at aerosol transport by speech as a possible mode of asymptomatic transmission”.
To analyse speech flow, he and his team modified a computer code they had originally developed to study the movement and behaviour of cumulus clouds – puffy cotton-like clouds that are usually seen on a sunny day. The code, called Megha-5, was written by S Ravichandran from NORDITA, the corresponding author on the paper. The analysis incorporated the possibility of viral entry through the eyes and mouth in determining the risk of infection. Post this finding, the team plans to focus on simulating differences in the loudness of speakers’ voices and presence of ventilation sources in their vicinity, to see what effect they can have on viral transmission.