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Infectious disease epidemiologist and microbiologist, aspirational barista. mlipsitc@hsph.harvard.edu Director @CCDD_HSPH

Jun 23, 2020 10:46 AM
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I agree with a lot of this thread. Primarily - in any time, but especially these days, it is inspiring to see a government agency release data, get bad press, and respond by releasing more data and asking for expert input.

Céline Gounder, MD, ScM, FIDSA (@celinegounder):
@NYChealthy took a beating in the @NYTimes over the weekend: https://t.co/vBE8zYYAul It’s a bit more complicated. Got an inside (but on-the-record) look at NYC’s #contacttracing data today, along with @MLipsitch, @T_Inglesby, @DSAllentess, @Farzad_MD, @DrJoshS, @TRVRB & others.

Also impressive was the evidently hard-working, experienced, resourceful team of people trying to make this program a success, and the consistent effort to confront unsatisfactory numbers with feasible means for improvement. Given mission to make TTI successful, very impressive

But I think behind the NYT story and behind other critiques of tracing for example https://www.nationalgeographic.com/science/2020/05/coronavirus-contact-tracing-covid-19-complex-health-investigation/

and and https://www.newyorker.com/news/us-journal/can-coronavirus-contact-tracing-survive-reopening

there is a bigger question. Many experts, often with experience in contact tracing in other diseases in other populations, have sold test-trace as the solution to how we reopen life while keeping SARS-CoV-2 in check. This was overconfident.

As noted on yesterday’s discussion, this is a disease with a natural history that is challenging for contact tracing, with most contagiousness before or a few days after symptoms. That makes it key to trace fast and with high success https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30361-3/fulltext

For this disease for now we have nothing medical to offer someone who is positive – NYC Is being innovative in trying to offer other forms of support, but “Congratulations! You now get to stay isolated for 2 weeks” is not good news for most people.

This chart from @celinegounder ‘s thread shows the challenges. 3797/7584=50% of known index cases completed interview. 2939/6672=44% of named contacts completed interview. This means at most (approx) 22% of transmissions could be captured with present performance.

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Add to that the cases not reported (historically in the US the estimated number seems to be 5-10x the reported number, probably not that bad now in NYC as more testing). That might add another factor of 2. And many cases are getting tested long after symptoms (anecdote from zoom)

And the tracing takes time. So based on what I learned yesterday, I would be surprised if contact tracing as now practiced is reducing transmission >5% in NYC. To be clear, 5% is something – and may be life and death to some individuals. This is valuable work, even with problems

Also to be fair, this is enormously hard, and data like these the first week are impressive, at least for the scale of what has so far been done and for the quality of thought about how to improve it (unlike reports from London).

As @CharlieBakerMA said in a press conference, we should be figuring out the challenges and improving performance of these systems while not in crisis so we will be better in a crisis. NYC is doing that.

But equally, we should recognize that the countries that have had great success with contact tracing didn’t reopen with 100s or 1000s of new known cases a day. Korea reopened with 5/day in 50m population. Europe reopened around 2/100K/day or less.

US is reopening with far higher per capita rates, often with less testing capacity (talking about the country now, not NYC). Contact tracing effort scales at least linearly with case burden, and effectiveness scales down proportional to undetected cases.