Thread by @AndrewALover, New UK strain of #COVID19 (B1.1.7) Suggested that it's 70% more transmissible. [...]

Andrew Lover

AndrewALover

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New UK strain of #COVID19 (B1.1.7)

Suggested that it's 70% more transmissible.

What if this is a "side effect" of massive levels of testing?

Surely mass testing/diagnostics can't drive evolution right? That's crazy.

Well.... it's already happened with malaria. 1/n

Most malaria rapid tests ("RDTs") target a protein called HRP-2 (histidine rich-protein 2).

Way back in 2010, some "oddball" parasites were found that were missing this protein, and therefore "invisible" to the rapid tests.

How were these discovered? By accident.

2/n

Most malaria rapid tests ("RDTs") target a protein called HRP-2 (histidine rich-protein 2). Way back in 2010, some "oddball" parasites were found that were missing this protein, and therefore "invisible" to the rapid tests. How were these discovered? By accident.2/n

Accident you say? The CDC was using banked parasites to QC rapid tests. The tests utterly failed with some parasites from Peru.

Head-scratching and sequencing found they didn't express the target protein (which was considered "essential"). 3/n

Accident you say? The CDC was using banked parasites to QC rapid tests. The tests utterly failed with some parasites from Peru. Head-scratching and sequencing found they didn't express the target protein (which was considered "essential"). 3/n

These "silent parasites" were only vaguely interesting, until.... 2015 when fatalities occurred in Eritrea (delayed treatment after false-negative rapid tests, with high parasitemia by microscopy).

https://malariajournal.biomedcentral.com/articles/10.1186/s12936-017-1752-9 4/n

Subsequent work suggest strong evolutionary pressure.

Undetected parasites..... aren't treated, & thus far more likely to be transmitted onward.

Modelling the drivers of the spread of P. falciparum hrp2 gene deletions in sub-Saharan Africa https://doi.org/10.7554/eLife.25008 5/n

Subsequent work suggest strong evolutionary pressure. Undetected parasites..... aren't treated, & thus far more likely to be transmitted onward. Modelling the drivers of the spread of P. falciparum hrp2 gene deletions in sub-Saharan Africa https://doi.org/10.7554/eLife.25008 5/n

Well... that's great and all, but malaria is malaria, and there are great drugs, so proper treatment is the main driver there.

Nothing to do with #COVID19, right? 6/n

But.... we quarantine and isolate using antigen-based rapid tests, and/or PCR.

If there is 𝙖𝙣𝙮 𝙨𝙡𝙞𝙥𝙥𝙖𝙜𝙚 in diagnostic performance, then these "new" strains are at an advantage. 7/n

But that's just hypothesizing, right?

well.. European CDC thinks it's a real concern.....

If detection decreases, then people with these infections are less like to be "captured" and into isolation, and contacts not followed up.

https://www.ecdc.europa.eu/en/publications-data/threat-assessment-brief-rapid-increase-sars-cov-2-variant-united-kingdom 8/n

But that's just hypothesizing, right?well.. European CDC thinks it's a real concern..... If detection decreases, then people with these infections are less like to be "captured" and into isolation, and contacts not followed up. https://www.ecdc.europa.eu/en/publications-data/threat-assessment-brief-rapid-increase-sars-cov-2-variant-united-kingdom 8/n

Tl,DR: Mass testing & diagnostics can exert significant evolutionary pressure so less-likely-to-be-detected pathogens have an epidemiological advantage that may or may not be based on virology. #COVID19

We need seriously consider implications and plan accordingly. NOW.

9/n

Tl,DR: Mass testing & diagnostics can exert significant evolutionary pressure so less-likely-to-be-detected pathogens have an epidemiological advantage that may or may not be based on virology. #COVID19 We need seriously consider implications and plan accordingly. NOW.9/n

And another example I wasn't aware of:
𝘊𝘩𝘭𝘢𝘮𝘺𝘥𝘪𝘢 𝘵𝘳𝘢𝘤𝘩𝘰𝘮𝘢𝘵𝘪𝘴

https://www.eurosurveillance.org/content/10.2807/ese.14.19.19206-en

https://twitter.com/ronansetron/status/1341095827759050753?s=20

Evidence for expansion of this variant?

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