On March 17, a Washington state public health office was notified that members of a choir turned sick after a rehearsal. In retrospect, it’s no surprise that so many people were infected with SARS-CoV-2 at a large gathering like that. At the time, the CDC hypothesized on the possibility that the act of singing might have accelerated this event, which already qualified as a superspreader. It turns out they were right.
The CDC was suggesting that loudness might increase aerosol emission. Simply put, the louder we speak or sing, the more tiny droplets come out of our mouths. What’s particularly dangerous is that these particles can remain in the air for a few hours and are capable of moving, meaning that social distancing becomes all the more important.
This particular incident prompted the scientific community to further study the topic. In the choir rehearsal, it was thought that one symptomatic person had spread COVID-19 infections to 52 other people (32 confirmed and 20 probable) — out of a total 61 present. (Such individuals who emit more aerosol due to a variety of reasons, like singing loudly, are called superemitters.) Tragically, three were hospitalized and two died. Back then, testing was relatively new in the U.S. and many weren’t fully aware of the gravity of the virus. The rehearsal lacked social distancing and masks, and ventilation likely wasn’t a priority, either. These bleak circumstances were likely exacerbated by the singing, as research later revealed.
Aerosol science expert Jonathan Reid and his colleagues in the UK have also scrutinized this case. Their tests have replicated the superspreading event as much as possible and have included singers singing into a funnel, which sampled and counted the number of aerosols emitted in an environment isolated from potential interferences. This is one factor that distinguishes their study from others, as many don’t have a “zero-background” of aerosol. To be sure of any potential variance, the scientists arranged for a wide array of genres to be performed - including rock, jazz, pop, gospel, soul, musical theater, choral and opera. The results demonstrated that vocal volume was the primary determinant.
From the quietest to the loudest ranges of speaking and singing, aerosol emission was calculated to increase as much as 30 times - a critical finding. Singing was also found to emit more aerosol than speaking, but this difference wasn’t significant. The risk of infection in very loud singing and speaking, then, can be treated the same. On the other hand, speaking or singing as quietly as possible were found to not differ significantly from breathing. The study also found that there was no significant variance between the different genres tested.
What does this mean for us? Yes, singing and speaking might not differ much in similar volumes, but singing often attracts a higher volume than speaking, suggesting that the act itself is riskier (unless you are singing something inherently soft, like a lullaby). Further, singing could prompt others to sing along, whereas there aren’t many reasons for people to speak collectively. Together, these could factor into an increased risk for collective gatherings. Music lovers should be aware, as such.
Note: The author of this piece has no expertise in the life sciences. Interested readers should consult the CDC’s findings (https://tinyurl.com/y2bsckvx) or other relevant media coverage for thorough information.