Virus transmission by aerosol transport during short conversations

TL;DR

This study uses direct numerical simulations to analyze how aerosol transmission during short conversations is affected by speech interactions, revealing that two-way conversations can reduce infection risk through jet interference effects.

Contribution

The paper introduces a detailed simulation approach to quantify aerosol transport during conversations, highlighting how speech interactions influence transmission risk and suggesting optimal interpersonal distances.

Findings

Two-way conversations reduce aerosol exposure compared to monologues.

Unequal speech contributions increase infection risk for the quieter speaker.

Small height differences can worsen transmission due to jet interference.

Abstract

Pathogens like the SARS-CoV-2 are transmitted not only through violent expiratory events like coughing, but also through routine activities like breathing/speaking/singing. We perform direct numerical simulations of the turbulent transport of potentially infectious aerosols in short conversations. It is shown that a two-way conversation significantly reduces the aerosol exposure compared to a relative monologue by one person and relative silence of the other. This is because the interaction of the jets ejected from the mouth of each speaker produce a "canceling" effect. Unequal conversation is shown to significantly increase the risk of infection to the person who talks less. Interestingly, a small height difference is worse for infection spread, due to reduced interference between the two speech jets, than two faces at the same level! For small axial separation, speech jets show large oscillations and reach the other person intermittently. We suggest a range of lateral separations between two people to minimize transmission risk. A realistic estimate of the infection probability is provided by including exposure through eyes and mouth, in addition to the more common method of using inhaled virions alone. We expect that our results will provide useful inputs to epidemiological models and to disease management.