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H-5 - Early A-B diversity reflects two or more separate zoonotic introductions, not one

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Properties11
type
hypothesis
id
H-5
state
active
question
Did SARS-CoV-2 enter humans through a single introduction or through two or more independent introductions?
statement
The two co-circulating early lineages A and B arose from at least two independent zoonotic introductions of SARS-CoV-2 into humans (both progenitor viruses circulating in non-human mammals beforehand), rather than from a single introduction that then diversified within the human population.
cluster
HC-2
source
S-1 - Pekar et al. 2022 — molecular epidemiology of multiple zoonotic origins of SARS-CoV-2
locator
S-1: Abstract; Discussion
merged_from
generalization_note
Folded in H-6 (no genuine intermediate A/B haplotypes circulated in humans; the apparent intermediates are contamination/bioinformatic artifacts, O-5) as a supporting sub-claim for the two-introduction reading, not a separate value of the introduction count. H-6 shares this node's source (S-1), so additional_sources stays empty.
quote
Early SARS-CoV-2 genomic diversity and epidemiology is best explained by at least two separate zoonotic transmissions

Central claim of the paper. Contestable and contested: a 2024 erratum reduced the supporting Bayes factor, and independent reanalyses (Weissman, McCowan) argue the corrected model actually favors a single introduction.

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