New research: The risk of Covid-19 transmission when two people are talking

Interactions of speech jets during short conversations between two people separated by a distance of 4 feet. (Source: Rohit Singhal, Indian Institute of Science)

For the simulations, the team visualised scenarios in which two maskless people are standing 2 ft, 4t or 6 ft apart and talking to each other for about a minute, and then estimated the rate and extent of spread of speech aerosols. The simulations showed that the risk of getting infected was higher when one person acted as a passive listener and didn’t engage in a two-way conversation. Factors like the height difference between the two people, and the quantity of aerosols released from their mouths, also appear to play an important role in viral transmission, IISc said in a press release.

For the analysis, the team modified a computer code (called Megha-5) they had originally developed to study the movement and behaviour of cumulus clouds. The analysis incorporated the possibility of viral entry through the eyes and mouth in determining the risk of infection, the release said, noting that most previous studies had only considered the nose as the point of entry.

When the speakers were either of the same height, or of drastically different heights (one tall and another short), the risk of infection was found to be much lower than when the height difference was moderate. Based on the results, the team suggests just turning their heads away by about 9° from each other while still maintaining eye contact can reduce the risk considerably.

Moving forward, the team plans to focus on simulating differences in the loudness of the speakers’ voices and the presence of ventilation sources in their vicinity to see what effect they can have on viral transmission, the release said.

(Source: IISc)