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One of the most common objections about retrospective (backward) contact tracing (i.e. Japanese style) is that it's too difficult.
You know what?
Prospective (forward) contact tracing (i.e. Korean style) is a lot more difficult.
THREAD
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You know what?
Prospective (forward) contact tracing (i.e. Korean style) is a lot more difficult.
THREAD
1/
#1 comes to work on Monday.
After lunch, he starts feeling a bit funny but he pushes through. Nov/Dec is the most intense period of the year.
But in the evening he has a fever.
On Tuesday morning, his rapid COVID test is positive. He calls the owner.
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After lunch, he starts feeling a bit funny but he pushes through. Nov/Dec is the most intense period of the year.
But in the evening he has a fever.
On Tuesday morning, his rapid COVID test is positive. He calls the owner.
2/
The owner figures out what happened. #1 had a fun 3 day golf weekend with 6 of his best friends. One of them must have been infectious, because by now most of them are symptomatic. See? Backward tracing is easy.
But what about the forward part? What about the workplace?
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But what about the forward part? What about the workplace?
3/
#2 had a couple of meetings in #1's office on Monday.
"Close contact": 6 feet for more than 15 minutes.
On Tuesday night, #2 is told to go get tested and quarantine at home.
#2 is asymptomatic/negative. There are no other close contacts.
Home free?
Sorry.
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"Close contact": 6 feet for more than 15 minutes.
On Tuesday night, #2 is told to go get tested and quarantine at home.
#2 is asymptomatic/negative. There are no other close contacts.
Home free?
Sorry.
4/
On Monday, #1 had a brief morning "huddle" with about 20 co-workers. It was less than 10 minutes and in a large common area.
So even though none are close contacts, the owner asks them all to go get tested over the next few days.
4 of them eventually test positive.
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So even though none are close contacts, the owner asks them all to go get tested over the next few days.
4 of them eventually test positive.
5/
The owner closed the workplace after Thursday and asked the rest of the employees to get tested. Not all got tested, but a lot did.
4 more employees called in with positive test results over the weekend.
At that point, the owner arranged for on-site testing.
6/
4 more employees called in with positive test results over the weekend.
At that point, the owner arranged for on-site testing.
6/
After several rounds of testing, a total of 20 people ended up being positive.
The owner learned a lot about COVID. He also learned way more than he wanted about the social lives of his employees: smoking breaks, lunches, parties.
But he did salvage the holiday season.
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The owner learned a lot about COVID. He also learned way more than he wanted about the social lives of his employees: smoking breaks, lunches, parties.
But he did salvage the holiday season.
7/
Lesson 1: COVID is faster than you think. Contact tracers often assume about 1 week for a new "generation" of cases (median incubation time ~5 days). But if we consider the golf weekend as the initial event, there were 3 generations in 1 week!
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We don't usually see this because tracing is slow. But look at the table at the bottom of this diagram of an outbreak at a Starbucks in South Korea. The initial exposure was Aug 8. By Aug 19, 54 cases (3 generations) had been diagnosed!
https://twitter.com/kj_seung/status/1296641197713362946?s=20
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https://twitter.com/kj_seung/status/1296641197713362946?s=20
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Lesson 2: You can test contacts too quickly and miss a case in the incubation period.
Multiple employees were neg initially but ended up testing positive later (including #2
).
Multiple rounds of testing will be needed when dealing with a large outbreak.
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Multiple employees were neg initially but ended up testing positive later (including #2
). Multiple rounds of testing will be needed when dealing with a large outbreak.
10/
Lesson 3: "Non-close" contacts can be infected too. The 20 people at the Monday huddle were not close contacts ("6 ft and 15 min") but 4 were infected.
If the owner had strictly followed CDC guidelines, he would have stopped after testing #2. It's a good thing he didn't!
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If the owner had strictly followed CDC guidelines, he would have stopped after testing #2. It's a good thing he didn't!
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When indoors, even non-close contacts can be infected. Many examples from Asia, but any experienced contact tracer has similar stories.
And yet, COVID is passed from one person to another. Those 4 infected people from the morning huddle? 3 were standing right next to him.
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And yet, COVID is passed from one person to another. Those 4 infected people from the morning huddle? 3 were standing right next to him.
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The definition of close contact isn't protective. It tells you who is most likely to be infected, not who won't be infected.
Perhaps we need another category: "low-risk contacts" or "remote contacts" who should be tested but not necessarily quarantined.
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Perhaps we need another category: "low-risk contacts" or "remote contacts" who should be tested but not necessarily quarantined.
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Lesson 4: Act decisively in the event of an outbreak. When the virus is widespread in the community, the virus will get into the workplace.
Businesses often argue whether it's workplace transmission or community transmission. That's a waste of time.
The answer is: YES.
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Businesses often argue whether it's workplace transmission or community transmission. That's a waste of time.
The answer is: YES.
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Quarantine quickly. Test more widely than just close contacts. Tell your employees and ask them to tell you about test results. Inform patrons about the exposure and tell them to get tested. The community will appreciate the transparency. Ignore those who try to shame you.
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Lesson 5: The Koreans are faster at contact tracing than you!
@nataliexdean @bridgethanna @samanthadoyle96 @BillHanage @aidancyr1 @cmyeaton @AdamJKucharski
@nataliexdean @bridgethanna @samanthadoyle96 @BillHanage @aidancyr1 @cmyeaton @AdamJKucharski
