The latest installment of the aerosol and singing study from the University of Colorado in Boulder was released on April 13, 2021. In this study, they examined multiple instruments, a singer, and a theater performer, but concentrated their findings on the singer and the clarinetist. They studied indoor conditions in a small, controlled room, and modeled outdoor conditions, which would include ambient wind. In general, using masks greatly reduced the aerosol plume in front the the singer and the player, but did not eliminate it entirely. Some leakage was found going behind the singer, near the ears, emphasizing the need for a good mask fit by the singer. (This would include the congregation, if there is to be congregational singing.) The researchers recommended any indoor rehearsals to be less than thirty minutes before vacating the room for an air change, and less than 60 minutes outdoors. Risk increased after these durations.

https://scholar.colorado.edu/concern/articles/hq37vp75r

 

Published March 29, 2021, this article from the BBC relying on the guidance of Professor Cathy Noakes, aerosol scientist in the UK, explains that outdoor transmission is very unlikely.

https://www.bbc.com/news/explainers-55680305

 

This study essentially states what we've known for awhile, that people can produce varying amounts of aerosol when they speak, smaller particles containing virus can remain airborne for quite some time, and that mask-wearing greatly reduces the aerosol plume released into the air. Published January 21, 2021.

https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciab039/6103221?login=true

 

Peer-reviewed and accepted for publication on September 26, 2020, this case study of the Skagit Valley choir case by aerosol and disease transmission experts posits that aerosol transmission is the most likely cause for the large outbreak of COVID-19 following the rehearsal. Several suggestions are made for making similar situations less risky. Members of the choir and the Skagit Valley Health Department provided detailed information on the rehearsal, which increased the accuracy of the modeling. OF NOTE: The authors mention that while the ballistic/large droplet transmission route is thought to be the most likely mode of transmission by many researchers, there is actually no direct evidence in any of the literature to support this. In other words, there's no reason to discount aerosol transmission when large droplet transmission doesn't have any more evidence.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/ina.12751

 

Twelve singers in an airtight chamber were observed speaking and singing at various pitch and loudness levels. Singing was found to produce more particles, and loud singing produced even more. The procedures were repeated with the participants wearing surgical masks, which reduced visible particles by a great amount. Interestingly, some of the participants were COVID-19 positive at the time of the experiment and no virus particles were found in the air during the experimental phase. There are numerous variables in this experiment that make it a little hard to build policy from, but it is interesting nonetheless.

https://www.tandfonline.com/doi/full/10.1080/02786826.2020.1812502

 

Harvard/Mass General Grand Rounds hosted Dr. Anthony Fauci on September 10, 2020. In the segment beginning at 15:40 Dr. Fauci specifically states that singing is a risk for transmission. Note too how he mentions at the segment beginning at 16:40 how the type of gathering, rather than a single person who may be a superspreader, is more likely to cause super spreading events. https://externalmediasite.partners.org/Mediasite/Play/52eeb2bcca3449e9bdc32d4dcd767d291d

 

The National Academies of Science hosted a webinar conference on August 26-27, 2020 that discussed what was known about the transmission of SARS-CoV-2. The proceedings of that meeting were recently released online. The video presentations are also still available at this link. This is a dense document, but has a great deal of information that can be useful in risk mitigation and understanding how the disease transmits. I would urge you to watch the excellent lecture by Dr. Linsey Marr, which is video #6 in the queue. Lecture #8 was also incredibly interesting, giving the origins of the droplets and aerosols from the respiratory tract. Basically, the smaller the particle, the lower in the respiratory tract it likely originated. This has implications for viral load, because the virus likely will be lower in the lungs rather than in the mouth, so smaller particles have the possibility to carry more viral load.

https://www.nap.edu/catalog/25958/airborne-transmission-of-sars-cov-2-proceedings-of-a-workshop

 

UPDATE: The preprint referenced below was peer-reviewed and accepted for publication on February 5, 2021. The final article version is here.

Non-peer-reviewed preprint posted August 20, 2020 from the PERFORM study, partially funded by the National Public Health of Great Britain. The authors tested singers performing multiple tasks at different volume levels and concluded that the volume at which a singer speaks or sings has a great impact on the amount of aerosols produced. At conversational levels (50-60 dB) the aerosols were similar to breathing, but grew in order of magnitude as the dynamic increased. Recommendations  that guidelines for public singing should be based on the dynamic level of the activity , rather than on the activity type.

https://chemrxiv.org/articles/preprint/Comparing_the_Respirable_Aerosol_Concentrations_and_Particle_Size_Distributions_Generated_by_Singing_Speaking_and_Breathing/12789221

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Summary of results from the PERFORM study and SOBADRA study. This is not a journal article, but rather a "consensus statement" by the researchers. I particularly find their degrees of confidence on certain conclusions helpful.

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/914628/S0695_Aerosol_and_Droplet_Generation_from_Singing__Wind_Instruments__SWI__and_Performance_Activities.pdf

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The second round of preliminary data from the University of Colorado in Boulder was released in a presentation on August 5, 2020.

https://www.youtube.com/watch?v=u8JgK-vA8Qc

0:00-7:52--study and personnel intro

7:52-11:00--video message from Dr. Shelly Miller about aerosols (corrected audio as the initial presentation was garbled)

11:00-18:24--Airborne Particle Spectrometer (APS) of oboe, trombone, low brass, theater performer, and singer

18:2430:08---Flow Visualization Explanation (note especially the videos of the trumpet and oboe toward the end of this section

30:08-37:33--Computational Fluid Dynamics modeling

37:33-39:10--Mask fitting data and recommendations

39:10---1:13:32--Considerations and recommendations

1:13:32-end--closing remarks

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NFHS webpage with links to the preliminary research releases from the UC Boulder/UMaryland study. This page is updated regularly with the release of new results.

https://www.nfhs.org/articles/unprecedented-international-coalition-led-by-performing-arts-organizations-to-commission-covid-19-study/

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Safer singing practices, published in Journal of Voice July 2, 2020. The charts in the middle of the paper are particularly helpful for gauging how to move toward the safer end of the continuum. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7330568/

 

The CDC released a review of the Skagit Valley Chorale outbreak, which posited that the social aspects of the rehearsal, such as stacking chairs together and sharing snacks may have been probably modes of transmission, while singing may have augmented the transmission. Published online May 15, 2020

https://www.cdc.gov/mmwr/volumes/69/wr/mm6919e6.htm?s_cid=mm6919e6_w

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Airborne particles in a stagnant air environment can be detected 8-14 minutes after speaking, making airborne transmission of virus particles from speech a "substantial" probability. I mentioned this study in Update #1, and highlighted the findings because this is very concerning. One thing I think we need to remember, however, is that most places, including church sanctuaries, are not completely air stagnant environments. However, knowing this it is important to be aware of the potential for infection from speaking, according to these researchers.

https://www.pnas.org/content/early/2020/05/12/2006874117

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Non-peer reviewed preprint from the University of Nebraska that observes possible airborne transmission of SARS-CoV-2 from infected patients at their medication center. Available online March 26, 2020.

https://www.medrxiv.org/content/10.1101/2020.03.23.20039446v2

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Aerosol emission and superemission during human speech increase with loudness.

This study in Nature from February 2019 is one of the most fundamental to helping us understand the potential dangers of our current situation.

https://www.nature.com/articles/s41598-019-38808-z

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An older article, vital lung capacity, likely from the expiratory phase of singing, is found to be significantly greater in choral singers than in non-singers. Published November 2016. (Vital capacity is the amount of air that can be exhaled after a person inhales their maximum amount. It can be measured in multiple ways. For an explanation of the different types of lung capacity, click here.)

https://www.sciencedirect.com/science/article/abs/pii/S0892199715001848

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