On TTI as a control measure:

Early 2020, we said contact tracing would not control community spread against #COVID19 once cases got high

Yet when cases got high, it was blasphemy to suggest lab PCR+contact tracing not useful to control spread.

Data is now catching up.

1/ https://twitter.com/epi_dude/status/1361992993222389765
The tweet thread above by Denis Nash @epi_dude is terrific and contains lots of wonderful data!

For me, It highlights the need for us to re-evaluate what it is we are doing. When our actions weren't working to slow spread, should we have kept forcing the same actions?

I worry that we get into group-think mentality and peer pressure is immense to "stick with the consensus"...

but when consensus is to stick to a failing test-trace-isolate as control, against our own warnings to our future selves... maybe we should've bucked the trend?

Virus kinetics are FAST for this virus

Peak virus load (and likely peak transmission) is 24-72 hours after first becoming at all PCR detectable

This swift transmission window, coupled w slow lab based PCR means contact tracing to control community spread was bound to fail

Forward contact tracing is good for some things, like identifying others around you who may have been infected but it is very unlikely to stop community spread.

I wrote about this in a thread based on a nice paper back in November.


When cases get very low, then contact tracing can start to work again, particularly backwards contact tracing, to help contain an outbreak.

But I wish we had shifted course long ago, placed less emphasis on lab PCR+contact tracing and more on widesclae rapid tests...

Widescale rapid testing can remove need for contact tracing from the equation.

If 50% of a community is already testing frequently (2x/week), then enough people will find out if they were infected and isolate far before a contact tracer would have gotten to them.

The swift window for transmission means that frequent use of rapid tests that give immediate results is very likely to be a major advance over infrequent laboratory based PCR. The latter simply didn't work. It's great for clinical medicine -but it's not a public health test

You can follow @michaelmina_lab.
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