The authors write: “There exists some evidence to suggest that singing can produce more aerosols than normal talking or breathing; it may be more akin to a cough.
“Singing for any appreciable amount of time therefore may present a risk for the creation of infectious aerosols and allow for infection transmission.”
Covid-19 is spread through respiratory secretions which can take the form of large droplets or smaller aerosols.
Singing may be as risky as coughing when it comes to spreading coronavirus, experts believe, crushing the hopes of choristers eager to join in harmony.
Singing – especially gatherings of large groups for a prolonged duration – should be viewed as a “more risky practice”, according to a paper discussed by the Scientific Advisory Group for Emergencies (Sage).
This is because of evidence that suggests the activity can produce more aerosols than normal talking or breathing.
These are either inhaled directly or transferred by the hands from surfaces where they have been deposited.
The smaller the particle, the further it can advance into the respiratory tract, the document says.
It is not clear if the playing of wind instruments presents the same risk.
More research is needed into the risk of transmission from both activities, they add.
Around two million people regularly sing in the UK and there are 70,000 choirs.
Public Health England and the Department for Digital, Culture, Media and Sport are coordinating a working group to explore safe resumption.
At present, social distancing remains the most effective way to reduce transmission, with rapid testing of participants prior to congregation not currently available and face masks not compatible with the activity, the paper says.
The authors write: “Even in outdoor settings, the wind can keep droplets airborne for longer and in a closely clustered arrangement where people are singing for a long period of time, this could still pose a risk.
“Therefore, at the present time the safest way for groups to sing together is to i) sing outside, ii) use the 2m rule to socially distance and iii) avoid face-to-face positioning.”
A separate paper considered by Sage recommends that performers in concert venues and theatres use more microphones.
There is evidence louder voices can produce more aerosols but it is not known if volume has an effect on how far they can spread.
Venues should keep the air well ventilated, restrict numbers of people in areas such as the foyer, bar and backstage and ensure surfaces are cleaned between performances.
They should also consider not using balconies, where the virus may build up, while staff members working on lighting rigs should wear masks.
And singalongs involving the audience for a significant period of time should be avoided.