Fine aerosols emitted during talking and singing may play a crucial role
in COVID-19 transmission: Singapore study
Landmark findings underscore the importance of reducing exposure to fine respiratory aerosols, especially in indoor environments

Date:
August 11, 2021
Source:
National University of Singapore
Summary:
A new study has revealed that severe acute respiratory syndrome
coronavirus (SARS-CoV-2) particles can be aerosolized by an infected
person during talking and singing. Researchers concluded that fine
respiratory aerosols may play 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.



FULL STORY ==========================================================================
The coronavirus disease 2019 (COVID-19) has been thought to spread
primarily when an infected person coughs or sneezes, but little is
known about its transmissibility through activities such as breathing,
talking and singing.


==========================================================================
A new study led by researchers from the National University of Singapore
(NUS), and conducted at the National Centre for Infectious Diseases
(NCID), revealed that severe acute respiratory syndrome coronavirus (SARS-CoV-2) particles can be aerosolised by an infected person
during talking and singing. They also found that fine aerosols
(less than 5 micrometres, or ?m) generated from these two types of
activities contain more viral particles than coarse aerosols (more than
5 ?m). The researchers concluded that fine respiratory aerosols may play
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-CoV-2 virus particles
generated. To our knowledge, 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 project leader Associate Professor Tham Kwok Wai, who is from the Department of the
Built Environment at the NUS School of Design and Environment.

The study was first published online in the journal Clinical Infectious Diseases on 6 August 2021. Within a day of its publication, the paper was ranked among the top 5 per cent of all research outputs scored by data
science company Altmetric, and was given one of the highest attention
score after different factors, like the relative reach from social media
sites, blogs, policy documents, and more, were taken into account.

Measuring SARS-CoV-2 particles in respiratory aerosols 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. This equipment was made available for this research by its inventor Professor
Donald Milton from the University of Maryland, who is one of the
co-authors of the paper and a collaborator on the project. 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 ?m) and fine (less or equal to 5 ?m). 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 from Duke-NUS Medical School.

"It has thus far been difficult to directly show how SARS-CoV-2 can
be transmitted. Through the coordinating efforts of one of our resident doctors, Dr Sean Ong, and the support of our nursing team and patients, we
were able to study key high risk activities like talking and singing while ensuring the safety of the patients and staff involved. The end result
provides direct 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 research also involved collaborators from the NUS Yong Loo Lin School
of Medicine's Departments of Microbiology and Immunology, Otolaryngology,
and Medicine, Tan Tock Seng Hospital, National University Health System,
as well as the Institute of Molecular and Cell Biology at the Agency
for Science, Technology and Research (A*STAR). It was supported by the Singapore National Medical Research Council and NUS.

Multi-layered approach for infection control 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.

"Although our attempts to grow infectious virus in cell culture were unsuccessful, our studies can provide an important baseline to guide
infection prevention activities," explained Professor Paul Tambyah from
the NUS Yong Loo Lin School of Medicine, who is one of the co-authors
of the research paper.

"In situations involving singing, safe distancing among singers, as
well as the averting and filtering of airflow from choir to audience,
such as by deploying air curtains, are important considerations. For
situations involving talking, determining airflow patterns and minimising exposure through seating and furniture configurations, distancing, and
air movement alteration, such as fans, including desk fans are practical options that can be taken to lower the risk of SARS-CoV-2 transmission," commented Assoc Prof Tham.

Further studies 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.

========================================================================== Story Source: Materials provided by
National_University_of_Singapore. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Kristen K Coleman, Douglas Jie Wen Tay, Kai Sen Tan, Sean Wei
Xiang Ong,
Than The Son, Ming Hui Koh, Yi Qing Chin, Haziq Nasir, Tze Minn
Mak, Justin Jang Hann Chu, Donald K Milton, Vincent T K Chow,
Paul Anantharajah Tambyah, Mark Chen, Tham Kwok Wai. Viral Load of
SARS-CoV- 2 in Respiratory Aerosols Emitted by COVID-19 Patients
while Breathing, Talking, and Singing. Clinical Infectious Diseases,
2021; DOI: 10.1093/ cid/ciab691 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210811131535.htm

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