SINGAPORE, Aug 11 — A new study led by Singapore researchers revealed that severe acute respiratory syndrome coronavirus (SARS-CoV-2) particles can be aerosolised by an infected person when talking and singing.
The researchers from the National University of Singapore (NUS) found that fine aerosols – less than 5 micrometres (μm) – generated from these two types of activities contain more viral particles than coarse aerosols – more than 5 μm.
The researchers concluded that fine respiratory aerosols might be playing a significant role in SARS-CoV-2 transmission, especially in an indoor environment, and hence, should be taken into consideration when planning infection prevention measures.
“While previous studies have established the relative amount of aerosols or the amount of particles produced through similar activities, they did not measure the amount of SARS-CoV2 virus particles generated,” said project leader Associate Professor Tham Kwok Wai in a statement today.
To their knowledge, Tham said this is the first study to quantify and compare SARS-CoV-2 particles in aerosols generated through breathing, talking and singing.
“Therefore, our team’s work provides a foundation for estimating the risk of transmission of infection,” said Tham who is from the Department of the Built Environment at the NUS School of Design and Environment.
The study which was first published online in the journal Clinical Infectious Diseases on Aug 6, 2021, involved 22 Covid-19 positive patients who were admitted to the National Centre for Infectious Diseases (NCID) from February to April 2021.
The participants had to perform three separate expiratory activities on the same day, 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.
“We observed that Covid-19 patients early in the course of illness likely to shed detectable levels of SARS-CoV-2 ribonucleic acid (RNA) in respiratory aerosols.
“However, person-to-person variation in virus emission was high. Some patients surprisingly released more virus from talking than singing,” said project co-leader Dr Kristen Coleman from Duke-NUS Medical School.
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.
As talking is the predominant community activity, the research team is also looking to establish the infectiousness of airborne aerosols, or live virus, emitted through talking by infected persons. — Bernama