What you need to know about the #PestisSecunda. A 🧵 for 2022.
Yesterday, I posed the question; "If we've been this ignorant about the largest pandemic in human history, on what kind of foundation are we basing responses now?"
I was referring to the #2ndPlaguePandemic. 1/n
Yesterday, I posed the question; "If we've been this ignorant about the largest pandemic in human history, on what kind of foundation are we basing responses now?"
I was referring to the #2ndPlaguePandemic. 1/n
For the past several years, I've been accustomed to saying that most people have a basic misconception of the Black Death (BD), the wave of plague that swept from the Black Sea thru the Middle East, N Africa, & Europe in 1346-53. People thought it came & then disappeared. 2/n
They didn't realize that the BD was the genetic foundation for all plague outbreaks that would strike the region periodically for the next 4-500 years. Cairo, Constantinople, Algiers, London, Seville, Marseille. And 1000s of towns & villages in betw. All due to same lineage. 3/n
What I've realized this past year is that that narrative may be slightly wrong. It's been clear since 2016 that at least 1 group of outbreaks in the "second wave" of Europe's plague era was caused by a lineage of Y. pestis that played no role in subsequent European outbreaks. 4/n
Up to this past year, it's been assumed that the main lineage that caused all subsequent European outbreaks, up to the famed Plague of Marseille/Provence in 1720-22, was a direct descendant of the Y. pestis lineage that arrived in Europe in 1347/48. Now, that story's changed. 5/n
Instead, a study that appeared in March 2021 presented evidence that the BD strains (which reached Europe in 1347-8) were different from "Lineage 1A," which was responsible for outbreaks from 1363 to 1722. Here's the phylogenetic tree, marked to show the separate clades. 6/n 
What does all this mean? These findings remain to be confirmed by geneticists & historians. But at the moment they suggest a parallel w/ our present moment. Pathogens given the freedom to proliferate will do so. Omicron may be our #PestisSecunda, an occult strain seeded ... 7/n
... early in the pandemic (in who knows what host or reservoir), only to emerge later. That it is less lethal than the 1st wave does not necessarily mean it causes less havoc. The BD seems to have left survivors numb. The 2nd wave left more recorded memories of trauma. 8/n
How is this a hopeful message from the past as we look out on a New Year? I find hope b/c it gives us a clear goal. Over 580,000 new COVID cases were reported in the U.S. yesterday. We need to stop transmission. We know how to do it. We just need to do it. #MaskUp 9/end
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