In August, German scientists invited a group of 1200 volunteers to attend a 10-hour long "concert" to learn more about the potential spread of coronavirus at live concerts. Upon arriving at the 8000-seat Leipzig Arena, every audience member underwent a standard-by-now virus-and-temperature check. They were each given a hand disinfectant laced with fluorescent dye, as well as a digital location tracker.
Over the course of the 10-hour experiment, the scientists than ran the crowd through numerous scenarios, using the dyes and location trackers as well as fog machines to trace physical contact and the spread of aerosols. As they explained in a new scientific paper published November 5 (but as of this writing, not yet peer reviewed):
Each scenario consisted of entry (60 minutes), 1st half (20 minutes, upscaled to 45), half time (20 minutes) including simulated catering, 2nd half (20 minutes, upscaled to 45), and exit (15 minutes). Contacts within a radius of 1.5 m were measured with a CTD. When all contacts (>10s) were considered, the number of contacts was high; when critical contacts with a duration of more than 15 minutes were counted (based on standard definition for contact tracing (18)) the numbers decreased below 10 (Fig 1a, Table S2).
So these scenarios included food/drink breaks, as well as bathroom runs. Some of them tested the effectiveness of jet nozzles to aid in air circulation. In some scenarios, the audience was socially distanced; in others, they were crammed together.
"High numbers of contacts were observed during entry and half time, but only few lasted more than 15 minutes," the scientists noted. Which is good news, and a potentially easy problem to avoid with staggered arrival times.
They also found that 10 times as many people would be potentially exposed to aerosols in standard ventilation conditions, compared to the scenarios where they used the jet nozzles. "We knew that ventilation was important but we didn't expect it to be that important," one of the scientists told The New York Times. Perhaps unsurprisingly, social distancing also reduced exposure.
Also from the Times:
Paul Linden, a professor of fluid mechanics at University of Cambridge, said that the computer modeling had not taken into account factors such as heat rising from an audience or indoor air turbulence, and that it was difficult to pinpoint whether it was the pattern of air flow or less ventilation in the venue that led to increased exposure to aerosols. As a general rule, he added, venues needed to bring in as much clean air as possible to lower transmission rates.
It's worth reiterating again that this study has not yet been peer reviewed. It was also performed at an 8000-person seated arena at nearly 1/8 capacity; so the results are less hopeful for people like me, who tend to go to concerts in smaller, non-seated venues (which aren't often known for their ventilation, even under good conditions). While I certainly know plenty of people who love the idea of a socially distanced concert, I personally find the thrill of a packed house to be a big part of the enjoyment of the experience (both as an audience member, and as a performer). Whenever small club shows resume, I suspect that masks will continue to be mandatory for a long time to come.
Coronavirus Study in Germany Offers Hope for Concertgoers [Isabella Kwai / New York Times]
To Test Spread of Coronavirus, These Scientists Put on a Concert [Thomas Rogers / New York Times]
Image: Lisdavid89 / Wikimedia Commons (CC 3.0)