Molecular evolution of Andes virus lineages leading to recent human outbreaks

Andes virus outbreak lineages in five human outbreaks are independently nested within geographically structured reservoir diversity, with closest sampled ancestry predating detection.

• Why it matters: It remains unclear whether recent person-to-person outbreaks reflect recent viral adaptation or the emergence of already circulating reservoir lineages.
• What they did: The team sequenced paired blood- and nasal-derived genomes from the MV Hondius outbreak, then combined them with a segment-linked human- and rodent-derived collection, using a linkage-informed missing-segment framework for sensitivity analyses.
• The result: Time-dependent-rate analyses support a deeper reservoir-associated history, while mutation reconstruction, selection tests, branch-rate comparisons, and structural mapping found no recurrent adaptive transition before human transmission, with MV Hondius showing minimal consensus-level diversification.

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