Watching someone blow out birthday candles during the coronavirus pandemic could lead to concerns that aerosols are spewing into the air. But you may have concerns over the tradition that comes shortly before the candles are extinguished, as singing “Happy Birthday” may also have us thinking about possible transmission of COVID-19, thanks to a Swedish study.
“Singing generated more respiratory aerosol particles and droplets than talking," researchers out of Lund University’s Aerosol Laboratory stated in their published study in the journal Aerosol Science and Technology.
The researchers also found that consonants are culprits in carrying aerosols while carrying a tune, according to the study, and many of the consonant letters they identified were discovered in the song "Happy Birthday."
“From the high-speed camera droplet analysis, we found that some consonants, for example, ‘P’, ‘B’, ‘R’, and ‘T,' generated a high number of small to large droplets," the researchers said in the published study.
“In particular, the enunciation of consonants releases very large droplets and the letters B and P stand out as the biggest aerosol spreaders," study author Malin Alsved, a doctoral student of Aerosol Technology at Lund University said in a press release.
In the study, participants entered a chamber full of filtered air, free of particles. Researchers conducted an analysis using a high-speed camera, strong lamps, and an instrument to measure small particles produced by performers as they were singing, breathing, talking, and then singing while wearing a face mask, according to a press release.
The release explained that the participants sang a Swedish song, “Bibbis Pippi Petter” repeatedly for two minutes and then sang the song again without the consonants, leaving only the vowels. The team of researchers then measured for the presence of aerosols, the mass of droplets, and distanced traveled by the air particles.
“The singing of vowels does not provide high airflows for the dispersal of particles, but as shown in the video file, the articulation of consonants expels droplets with considerable forward velocity. Nevertheless, most of the largest droplets travel a limited distance (<0.5 m) before their movement become vertical due to sedimentation," the published study stated.
“Some droplets are so large that they only move a few decimeters from the mouth before they fall, whereas others are smaller and may continue to hover for minutes,” Alsved said in the study release.
The researchers also explored the singing in patients infected with the novel coronavirus.
“We also carried out measurements of virus in the air close to two people who sang when they had COVID-19. Their air samples contained no detectable amount of virus, but 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," Alsved said in the press release.
When singing “Happy Birthday," be wary of loudly you sing and the pitch you sing the tune at in an effort to avoid transmission, per the researchers.
“Exhaled aerosol particles and droplets increased with song loudness,” the researchers stated in the published article. The report also noted that higher pitches emitted more particles.
The study also pointed out that wearing a face-covering can help contain the spread of aerosols.
The study also addressed the importance of face masks to prevent transmission of the droplets and the virus.
“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," study author Jakob Löndahl, an associate professor of Aerosol Technology at Lund University, said in the release.
Whether singing "Happy Birthday" at home or in a group activity, the authors concluded that singing in groups does increase the risk of transmission of the virus but said risk can be mitigated with the use of wearing face masks, social distancing, proper ventilation and hand hygiene.