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Infectious Diseases

14 September 2020

Coronavirus: Sing with physical distancing in place, caution researchers

Researchers studying the aerosol spread of the virus found that loud singing may cause infected aerosol particles to linger in the air.

  • Swedish researchers investigated whether singing is safe during the Covid-19 pandemic
  • According to their findings, loud, consonant-rich singing can lead to aerosol and droplet spread of the virus
  • This doesn't mean singing events should be put on hold, but simply that safe, protective measures must be in place

The arts and creative sectors have been badly hit by the Covid-19 pandemic, suffering large economic losses. But, as governments around the world are winding down lockdown measures, these sectors have started opening up.

Researchers who have studied whether singing plays an important role in spreading SARS-CoV-2, the virus that causes Covid-19, found that aerosol particles and droplets – emitted via singing – can spread through the air. However, this doesn’t mean singing should be entirely avoided. Instead, they caution that sufficient physical distancing measures should be in place.

The research team, from Lund University in Sweden, studied the number of particles emitted when singing. Their results were published in the journal, Aerosol Science and Technology.

Bigger than aerosols

"There are many reports about the spreading of Covid-19 [virus] in connection with choirs singing. Therefore, different restrictions have been introduced all over the world to make singing safer,” said Jakob Löndahl, associate professor of Aerosol Technology at Lund University.

The virus has been confirmed to spread via respiratory droplets, which are bigger than aerosols and travel relatively short distances. Aerosols, on the other hand, can accumulate in poorly ventilated areas and are carried by air currents.

To find out how many aerosols and virus particles we emit when we sing, Löndahl and team had 12 healthy singers (seven of them professional opera singers) and two people with confirmed Covid-19 take part in a research project, at the university’s laboratory.

The singers all wore clean air suits and entered a specially-built chamber that was supplied with filtered, particle-free air, and sang a short, plosive-rich Swedish song named "Bibbis pippi Petter".

The singing was repeated 12 times in two minutes at constant pitch. The number and mass of particles emitted by the singers during breathing, talking, different types of singing and singing with a face mask were noted.

Louder singing produces more aerosols and droplets

According to the findings, the louder and more powerful the song was, the greater the concentration of aerosols and droplets. Particularly loud and consonant-rich singing were also found to spread a lot of aerosol particles and droplets into the surrounding air.

"Some droplets are so large that they only move a few decimetres from the mouth before they fall, whereas others are smaller and may continue to hover for minutes,” explained Malin Alsved, doctoral student of Aerosol Technology at Lund University, adding:

“In particular, the enunciation of consonants releases very large droplets and the letters B and P stand out as the biggest aerosol spreaders.”

Regarding the two people who were Covid-19 positive and also sang, Alsved said that measurements of the virus in the air close to them were also noted, and that their air samples contained no detectable amount of virus. However, “the viral load can vary in different parts of the airways and between different people. Accordingly, aerosols from a person with Covid-19 may still entail a risk of infection when singing," said  Alsved. 

Should singing be allowed?

If physical distancing, good hygiene and good ventilation (which reduces the concentration of aerosol particles in the air) are in place, then singing events don’t have to be restricted, say the researchers. 

They also drew on the effectiveness of face masks: "When the singers were wearing a simple face mask, this caught most of the aerosols and droplets and the levels were comparable with ordinary speech," said Löndahl.

"Singing does not need to be silenced, but presently it should be done with appropriate measures to reduce the risk of spreading infection.”

Previous study, similar findings

In addition to this study, Health24 previously reported on a recent study that also investigated the number of aerosols and droplets expelled by a group of professional performers in an orthopaedic operating theatre.

According to the researchers of that study, singing is no more likely to spread infected aerosols and respiratory droplets than speaking at a similar volume.

The researchers recommended that live musical performances resume during the pandemic, but that special attention be paid to the type of room in which the activity occurs, and the duration of the performance, among other things.