So where did this definition come from? Well, you need to have a definition of what close contact is in order to do contact tracing. ANY kind of contact, no matter how incidental, would multiply contacts to the point that tracing becomes impossible.
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Let's say you go into a grocery store with 50 other people for 30 minutes. During that time, you run into someone you know and chat withing 6 feet for 15 minutes and then later find out you're positive for SARS-CoV-2.
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Using this definition, contact tracers will call the person you chatted with. Let's say then you went to your 10-person office and were around 5 of your coworkers within 6 feet for a longer period of time. No problem, contact tracers call another 5 people.
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Now let's say the definition of close contact is being ANY distance from people for ANY length of time. Suddenly contact tracers are calling 60 people. If transmission overall is low, that's still no problem. But that's not the situation in many places, including the US & Canada.
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With hundreds or thousands of new COVID cases per day, this quickly becomes an insurmountable task just based on the numbers. With 100 cases/day in a community, this becomes 6000 contacts. With 1000 cases/day, it's 60,000. And contact tracing is more than just calling contacts.
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So add to that the challenges in contact tracing: people don't always remember or know all their contacts or accurately recall where they were and when and for how long. Valid concerns about privacy may also make people reluctant to share this information.
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So, it's not perfect, but close contact is defined to allow contact tracers to follow up on exposures that are most likely to lead to infection. Defining close contact for this purpose is NOT, however, a hard line over which transmission cannot occur.
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Transmission is situational. If you are exposed to enough virus by the proper route, you can become infected. It can take less than 15 minutes to be exposed to enough virus. Depending on conditions, you can be exposed to an infectious dose over 6 feet away.
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This is true for all viruses, not just SARS-CoV-2, and not just B.1.1.7 or other variants. So we should not regard definitions of contact for tracing to be the definition of exposure risk as we live our lives. The conflation of these two is one of many communication failures.
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Now, with regard to B.1.1.7 being transmitted "faster", that's really hard to say. We only know that it's more transmissible, but not the mechanism. In other words, we don't know HOW it is more transmissible.
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don’t we have evidence that there are literally an order of magnitude (or more) viral particles? isn’t that a mechanism?
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