A (very long) thread on testing, the current scenario, and what ails us from testing more.

TL;DR version - unlikely to be able to do mass-scale testing w status quo. Need to experiment w currently avl test, or develop radically new tests. (1/n)
The WHO mantra has been "Test, test and test"+"test, track and trace". Test=genetic test btw, not serology. Great idea, and I& #39;d say thats how China, Korea managed to keep the lid on. BUT they caught it early, so worked. Why are other countries struggling to ramp up tests? (2/n)
For contact tracing to work, you need to identify every last case. Easier when you have fewer cases ("catch cases early! stop the spread!!" sounds familiar?). Else, there& #39;s way too many silent, asymptomatic spreaders to track. So, end up having to test most/full populations (3/n)
Now, can you employ test at scale? No. Why? Because the test is complex (see explainer thread). Again, by "test" - I mean the genetic test where you catch *currently* infected people and tell them to quarantine so they dont spread it to anyone else. (4/n) https://twitter.com/iamgkadam/status/1242242587999776770?s=20">https://twitter.com/iamgkadam...
This test needs many chemicals - aka "reagents" - that come in "kits", basically a set of all the reagents needed. Made mostly only by handful of companies, only 3 of them big, multinationals.

@ASMicrobiology did call this out quite early in March.
(5/n) https://asm.org/Articles/Policy/2020/March/ASM-Expresses-Concern-about-Test-Reagent-Shortages">https://asm.org/Articles/...
How much testing do we really need? Just focusing on one country (US), experts say we need 2x-6x current testing levels to go back to "normalcy" and regular life (8/n) https://www.politico.com/news/2020/04/22/coronavirus-testing-problem-america-201372">https://www.politico.com/news/2020...
And remember, need to do repeat testing of same person everyday/every few days to catch infected person and their contacts early & prevent spread. So, really need a crazy lot of testing! Insane, right? Even more when you consider the whole world - thats ~20x US population. (9/n)
If you are a NZ or a HK where you havent had cases for days and weeks, then you can stop testing. Until then, you need to - to be sure its not lurking somewhere hidden/spreading asymptomatically.

Now, can we even achieve that level of testing theoretically? (10/n)
There are 3 big global manufacturers of these reagents and kits essential to the test - Qiagen, Roche and Biomerieux. Many more smaller ones (Zymergen et al), but too tiny in comparison to make much of a dent afaik.

How much can the big 3 make? (11/n)
Qiagen says they can ramp up to 6.5mn kits a month by April, and 10mn/mo by June. Say, the other two are similar-ish. Thats about 40-50mn/mo.

That is *per month*. We need to do, just for US, 6mn/day*30d = 180mn. Huge gulf!

Image source: https://www.sciencemag.org/news/2020/03/standard-coronavirus-test-if-available-works-well-can-new-diagnostics-help-pandemic
(12/n)">https://www.sciencemag.org/news/2020...
Finally, an appeal - I led a team in this hackathon, and we have a very promising idea here based on antigen-testing, looks like a pregnancy test and can be mass produced quite cheaply. Looking for partners to do R&D now, pls reach out if interested /end https://youtu.be/-bMmMI3cfZM ">https://youtu.be/-bMmMI3cf...
Addendum: Nice review just out listing various scientific strategies being tried and developed in our quest towards Covid19 diagnostics.

Note - a very technical read. https://twitter.com/sgarakyaraghi/status/1256246109133029377">https://twitter.com/sgarakyar...
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