Friday, October 21, 2022

The legacy of the flea

BBC relayed a few articles about Yersinia lately. One was ERAP2 - this is an immune-system tweak which improved your resistance (to the AD 14th century version) 40%.

ERAP2 has also led to Crohn's. I think the latter is common to us the Ashkenaz although I might not have ERAP2 myself.

I've been reminded also of this. In 2018 was claimed that the disease spread amongst humans via lice, not fleas: that is, among humans rather than between humans via rat. At least: once brought into a city. This at least was done via computer-model so should apply to any plague outbreak including Justinian's, even the Neolithic's.

I expect that if the vaunted Jewish purity had helped, they'd not need the ERAP2 mutation. To me all this implies that Jewish neighbourhoods (and shtetls) were hit just as hard as were Gentile neighbourhoods. My nonERAP2 ancestors might have been more exurban than urban.

I also must wonder if ERAP2 had first expressed itself in Justinian's time. I suspect not, if Crohn's had not appeared before the 14th century. That plague kept resurfacing - relevant here, in the AG 940s / AH 630s Plague of Ammaus. Then most densely-populated cities became suddenly less dense, also more-suspicious of incoming boats and caravans.

RATS 1/17/2024 A nonreproducible.

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