What Do We Know About Events Related to the Spread of Coronavirus

On March 10, a choir in Washington state decided to continue the practice amid growing reports of the spread of the coronavirus in the United States. This rehearsal, which was attended by 61 of the usual 122 choir members, lasted two and a half hours, the participants took precautions. don’t communicate too much. Ultimately, according to a recent CDC report on the event, roughly 87% of the attendees later fell ill.

Choir practice is one of the best examples of such a large-scale event, says Pratit Kulkarni , MD, infectious disease specialist at Baylor College of Medicine. A hyperproliferation situation is defined as a situation where one person infects a large number of other people in a single event .

Choir practice is a prime example of overexploitation during the current pandemic, but there have been others – notably cruise ship and funeral gatherings, an international conference, and a women’s prison . While in these cases it is more difficult to pinpoint the single sick person who triggered the outbreak, they still fit because we know they have all led to a large number of infections.

As scary as the super-propagating event sounds, they are already rolled into a medium transfer rate. Some infected people can get sick in many people – for example, during choir practice – while most people get sick with only one or two. The average estimated transmission rate of the virus is known as its R 0 . The R 0 of the coronavirus is estimated to be in the range of 2.0 to 2.5, which means that on average one person will infect 2.0 to 2.5 other people, taking into account super-spreading events.

High density of people in enclosed spaces increases the risk of transmission

As noted by Kulkarni, it is the density of people in an enclosed space and / or the time during which they are in an enclosed space that lead to an increased risk of infection. During the choir practice, a large number of people were together in a closed room for several hours.

On the Diamond Princess cruise, 700 of the 3,711 passengers and crew fell ill – another environment in which everyone was confined to one space (albeit much larger, more isolated). It’s the same with the women’s prison in Louisiana , where nearly all of the inhabitants of one particular dormitory have tested positive for COVID-19.

“In these closed environments, where people are together for long periods of time, there is definitely a possibility that a large number of people will potentially become infected,” says Kulkarni. In general, the longer people are together, the more likely they are to become infected , whether through contact with respiratory droplets during a face-to-face conversation, shaking hands with an infected person, or touching an infected surface.

Biogen conference: two days of communication, participants return home

Another notable example, which occurred in late February, when there were still relatively few cases in the US, was the Biogen conference in Boston, which eventually resulted in approximately 99 cases, both among the participants and among the people with whom they later came into contact.

The infections resulting from the conference, during which large numbers of participants met repeatedly over two days, were compounded by the fact that the participants returned to their communities, both in the US and around the world, where they fell ill. …

As Kulkarni notes, the Diamond Princess cruise, the Louisiana prison and the Biogen conference are all variants of a super-propagating event, although all cases cannot be attributed to a single infected person.

Isolation and quarantine are effective measures to restrict transmission

Good news? Although a large percentage of the choir practice participants fell ill, it did not have a significant impact on transmission in the larger community , in large part because all participants acted quickly, initiating their own isolation and quarantine even before healthcare workers got it. involved. Measures such as hand washing, wearing masks, physical distancing practices, quarantine if infected, and isolation if symptoms develop are effective in limiting the overall level of infection – even after an overexplosive event.

“These are still best practices and best mechanisms that we must try to prevent the spread,” says Kulkarni.


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