The study involved 22 COVID-19 positive patients who were admitted to the NCID from February to April 2021. The NCID was the research site that selected and recruited the patients, and performed whole genome sequencing to determine their viral strains of infection. The participants had to perform three separate expiratory activities on the same day. These activities involved 30 minutes of breathing, 15 minutes of talking in the form of reading aloud passages from a children’s book, and 15 minutes of singing different songs, with rest between activities.
The participants had to carry out these three activities using a specially designed exhalation collection equipment known as the Gesundheit-II. In the studies, participants were required to place their head at the cone-shaped inlet of the equipment. This cone served as a ventilation hood where air is continuously drawn around the participant’s head, allowing the collection of expiratory particles into the connecting sampler.
Aerosols were collected in two size fractions, namely coarse (more than 5 μm) and fine (less or equal to 5 μm). The sample viral load was quantified by using a method known as reverse transcription-quantitative polymerase chain reaction.
“We observed that COVID-19 patients who are early in the course of illness are likely to shed detectable levels of SARS-CoV-2 RNA in respiratory aerosols. However, person-to-person variation in virus emission was high. Some patients surprisingly released more virus from talking than singing,” shared project co-leader Dr Kristen Coleman fromDuke-NUS Medical School.
"The end result providesdirect measurements to show that besides respiratory droplets, virus particles emitted in exhaled breath and vocalisation activities are likely important mechanisms for transmitting SARS-CoV-2," said Dr Mark Chen, Head, NCID Research Office, National Centre for Infectious Diseases.
The findings of this study demonstrated that exposure to fine-particle aerosols needs to be mitigated, especially in indoor environments where airborne transmission of SARS-CoV-2 is most likely to occur. Reducing exposure to fine respiratory aerosols can be achieved through non-pharmaceutical interventions, such as universal masking, physical distancing, increased room ventilation, more efficient filtration and appropriately applied air-cleaning technologies.
In particular, the research team recommended a multi-layered approach of control measures to decrease the risk of airborne SARS-CoV-2 transmission. In view of more recent variants of the coronavirus, especially the Delta variant which has been reported to be more infectious, the researchers plan to use the same methods to determine if the aerosol viral load associated with the new variants, especially the Delta variant, is higher than previous strains.
MEDICA-tradefair.com; Source: National University of Singapore
