Effect of different types of speech sounds on viral transmissibility: a scoping review

Previous evidence suggested that the phonetic features of a given language may modulate the quantity of droplets emitted from the mouth during speech, determining viral transmissibility. This scoping review aims to present the body of research with respect to the effect of different types of speech sounds on the potential transmission of a virus and to evaluate the certainty of evidence of these data. Five online databases were used to extract experimental research studies which were published between 2000 and 2021. Of the 2217 studies initially identified, 11 studies were included in the review. Each individual study was assessed with GRADE to detect their certainty of evidence. Most of the studies focused on the investigation of fricatives and plosives. It was found that plosives might have the most chance to transmit a virus, followed by nasals and fricatives. This chance is significantly reduced for vowels. The majority of the studies were of low or very low evidence. The results can allow epidemiologists to better model the factors that account for potential viral transmission by considering the effect of speech sounds. In addition, they can inform educators and clinicians for better management and reduction of the risk of viral transmission. The evidence provided about how specific speech sounds may contribute to the spread of a virus is very limited and is confined to the investigation of a few types of sounds. © 2021 Informa UK Limited, trading as Taylor & Francis Group.