SARS-CoV-2 transmission: How important is ‘super-spreading’?
Written by Erika Watts on November 6, 2020 — Fact checked by Rita Ponce, Ph.D.
A new study suggests that COVID-19 super-spreading events are more common than originally believed. Limiting gatherings to 10 or fewer people could help prevent this issue.
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Scientists have spent the better part of the past year trying to make sense of the novel coronavirus, SARS-CoV-2, which causes the disease responsible for the ongoing pandemic.
As COVID-19 cases approach 49 million worldwide, researchers continue to study how the virus spreads in an effort to find ways of reducing the transmission.
A new study from researchers at the Massachusetts Institute of Technology (MIT), in Cambridge, examines the spread of COVID-19 in large gatherings. It shows that super-spreading events are more common — and have more impact on the overall spread of the virus — than previously thought.
In their study paper, published in Proceedings of the National Academy of Sciences, theresearchers explain that these events have an “outsized” role in virus transmission.
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‘Super-spreading events’ defined
On average, SARS-CoV-2 spreads from one person to two to three others. In some cases, the virus does not transmit. But it can pass to dozens of other people in a relatively short period.
A super-spreading event is a gathering where the virus transmits from one person to several others. The researchers behind the present study considered super-spreading to take place when at least six people acquired the virus.
One such event, a choir practice, took place in Skagit County, WA. Scientists tracked 53 cases of COVID-19 back to one person with a SARS-CoV-2 infection at the rehearsal.
Of the 61 people who attended the 2.5-hour event, 33 tested positive for COVID-19 and 20 others had probable cases.
Since COVID-19 primarily transmits through respiratory droplets, the choir practice was a prime environment for it to spread.
Some other notable COVID-19 super-spreading events include the White House’s Rose Garden event where 35 out of approximately 200 attendees acquired the virus and a birthday party in Westport, CT, where 20 of the 50 partygoers acquired the virus.