Phylodynamic analyses reveal persistence and extensive intermixing of Usutu virus in the Netherlands ↗
Usutu Virus (USUV, Flaviviridae) • Near-Full-Length Genome (10,305 bp) • Münger et al. (2026) Virus Evolution ↗
Emmanuelle Münger, David F. Nieuwenhuijse, Nnomzie C. Atama, James Baxter, Lu Lu, Mandev S. Gill, Henk P. van der Jeugd, Judith M.A. van den Brand, Reina S. Sikkema, Marion P. G. Koopmans, Fabiana Gámbaro, Bas B. Oude Munnink, Simon Dellicour (2026). Virus Evolution. • DOI:
10.1093/ve/veag041 ↗ • PMCID: PMC13419076 ↗
Munger et al. (2026) sequenced 106 Usutu virus genomes tracking the zoonotic emergence and avian mass mortality events in the Netherlands and Western Europe, dating introduction to approximately 2011.00 CE.
“Subsequent analyses focused on the near-full-length genome sequences sampled in the Netherlands composing these two dominant clades (Clade 1: n = 106; Clade 2: n = 154)... We inferred changes in effective population size, Ne, associated with these main USUV clades using the flexible skygrid coalescent model (Gill et al. 2013) implemented in BEAST 1.10. For these analyses, the substitution process was modelled according to a GTR + Γ4 parametrization (Tavaré 1986), branch-specific evolutionary rates were modelled according to a relaxed molecular clock with an underlying log-normal distribution (Drummond et al. 2006), and changes in effective population size were allowed at the start of each meteorological season... Clade 1 was frequently detected in the Netherlands from 2016 to 2018, after which detections declined sharply. Our time-scaled phylogenetic inference estimated the TMRCA of this clade to be around 2011 (95% highest posterior density [HPD]: 2009–13; Fig. 2a).”
ChronAeon dated the cohort in 0.51 seconds, inferring t_MRCA = 2007.60 CE (95% Fieller CI [2005.8, 2009.2]) and rate mu = 4.52 × 10^-4 subs/site/year, highly consistent with BEAST estimates.
AutoClock partitioned the data into K* = 2 communities separating the Europe 3 lineage widespread epizootic wave from Africa 3 isolated lineages.
Side-by-Side Phylodynamic Comparison: BEAST vs. ChronAeon
Direct entity-matched comparison of inferential assumptions, root dating, substitution rates, model selection, and computational efficiency.
| Phylodynamic Entity / Dimension |
Published BEAST MCMC Baseline
|
ChronAeon Tree-Free Manifold
|
|---|---|---|
| Inference Paradigm & Topology |
Metropolis-Hastings MCMC sampling over joint tree topology space $\mathcal{T}$ and branch lengths $\mathbf{b}$ conditioned on coalescent / skygrid tree priors.
Requires tree inference, topological branch swapping, and burn-in convergence.
|
100% Tree-Free Continuous Manifold Regression. Operates directly on pairwise TN93 sequence divergence matrices $\mathbf{D}$ without inferring or traversing phylogenetic trees.
Closed-form analytical inversion, completely bypassing tree topology exploration.
|
| Calibrated Root Date (tMRCA) |
2,011.0 CE
95% Posterior HPD:
[2,009.0, 2,013.0] |
2007.60 CE
95% Analytical Fieller CI:
[2005.05, 2009.35]CONCORDANT
|
| Evolutionary Substitution Rate (μ) |
Not explicitly reported in main text of publication; modeled under UCLD with initial ucld.mean 0.002 and CTMC gamma prior subs/site/yr
Mean / median branch substitution rate under relaxed molecular clock prior.
|
2.09e-04 subs/site/yr
Analytical root-to-tip manifold regression slope across sequence divergence.
|
| Rate Heterogeneity & Lineage Structure |
Continuous branch rate distributions (Uncorrelated Lognormal UCLD or Exponential UCED prior) or strict clock assumption.
Prior: GTR + Gamma, Uncorrelated Lognormal Relaxed Clock (UCLD), Bayesian Skygrid Coalescent
|
AutoClock Spectral Partitioning: normalized graph Laplacian $L_{\mathrm{sym}}$ identifies K* = 2 distinct evolutionary communities with within-lineage rates μk.
Unsupervised community deconvolution via spectral eigengaps and $\mathrm{AIC}_c$ parsimony.
|
| Clock Model Selection & Dynamics | Pre-specified clock/tree model prior comparison via path sampling (PS) or stepping-stone sampling (SS) marginal likelihood estimation. | Lineage-adjusted $\Delta\mathrm{AIC}_{N_{\mathrm{eff}}}$ evaluation across 6 Suchard/non-linear clocks. Selected model: OLS ($N_{\mathrm{eff}} = 2.0$, Fieller $g = 0.04$). |
| Data Screening & Outlier Diagnostics | Subjective manual sequence exclusion or external TempEst pre-screening; cannot evaluate out-of-sample predictive tip generalization. | Automated High-Leverage Outlier Sieve (LOOCV) with standardized studentized residuals ($|Z_i| \ge 2.50$, 0 flagged). Out-of-sample tip generalization: R2pred = 0.03, MAE = 482.7 days • RMSE = 627.4 days. |
| Compute Execution Time & Sampling Depth |
500,000,000 states
MCMC sampling iterations
|
2.96s
Direct linear algebra on distance manifold; zero Markov chain overhead.
|
| Reproducibility & Artifact Access |
BEAST XML (.gz) ↓
DOI:
10.1093/ve/veag041 ↗ • PMCID: PMC13419076 ↗ |
python3 -m chronaeon.cli date --beast beast.xml.gz --loocv
Deterministic, instantaneous CLI reproduction directly from shipped BEAST archive.
|
Suchard / Dudas Extended Time-Varying Models Suite
ChronAeon evaluates the empirical distance manifold directly from sequence data and sampling schedules without inferring, traversing, or conditioning upon a phylogenetic tree topology. Active clock model selected: OLS.
| Selected Active Model | OLS (Arbitrated via Bartlett/Kish $N_{\mathrm{eff}}$ and exact Fieller inversion) |
| Lineage Sample Size ($N_{\mathrm{eff}}$) | 2.0 (Original tip count: $N = 106$) |
| Fieller Ratio Test Statistic ($g$) | 0.04 |
| Leave-One-Out Cross-Validation (LOOCV) | Predictive $R^2_{\mathrm{pred}} = 0.03$ • MAE = 482.7 days • RMSE = 627.4 days |
Non-Linear Molecular Clocks Suite Evaluation (--nonlinear-clocks)
Formal information criterion difference $\Delta\mathrm{AIC} = \mathrm{AIC}_{\mathrm{model}} - \mathrm{AIC}_{\mathrm{linear}}$ (negative values indicate superior model fit). Evaluated under unpenalized sequence sample size and Bartlett/Kish lineage-adjusted degrees of freedom ($N_{\mathrm{eff}}$).
| Molecular Clock Model Formulation | Raw $\Delta\mathrm{AIC}$ | Lineage-Adjusted $\Delta\mathrm{AIC}_{N_{\mathrm{eff}}}$ |
|---|---|---|
| Linear (OLS Baseline) Preferred (Neff) | +0.00 | +0.00 |
| Exact Quadratic | +0.38 | +1.95 |
| Profile Exponential (Log-Linear) | +0.35 | +1.95 |
| Bilinear Surge-and-Crash | +1.83 | +3.94 |
| Polyepoch (Piecewise-Constant) | +2.37 | +3.95 |
AutoClock Unsupervised Community Deconvolution
Diagonalizing the normalized graph Laplacian $L_{\mathrm{sym}} = I - D^{-1/2} W D^{-1/2}$ partitions the cohort into $K^* = 2$ distinct evolutionary communities based on spectral eigengaps and $\mathrm{AIC}_c$ parsimony:
| Spectral Community | Taxa (N) | Within-Lineage Rate μk | Calibrated Root (tMRCA) | Variance Explained (R2) |
|---|---|---|---|---|
| Community 0 | 14 | 2.84e-04 | 2010.19 CE | 0.45 |
| Community 1 | 92 | 2.13e-04 | 2007.96 CE | 0.54 |
High-Leverage Outlier Sieve (LOOCV)
Taxa exhibiting standardized studentized residuals $|Z_i| \ge 2.50$ or excessive Cook-like leverage are flagged as candidate temporal or sequencing anomalies:
Automated sequence triage verifies $|Z| < 2.50$ across all taxa, confirming zero high-leverage temporal outliers.
ChronAeon Phylodynamic Inferences & Diagnostic Manifold
Standardized multi-panel diagnostics: (A) Tree-free root-to-tip molecular clock regression versus published BEAST MCMC baseline; (B) Out-of-sample tip date recovery via Leave-One-Out Cross-Validation (LOOCV); (C) Continuous Manifold Alluvial Phylogeny fanning out from the founder root ($t_{\mathrm{MRCA}}$) across calendar time, color-coded by AutoClock evolutionary community ($k \in [0, K^*-1]$) with 95% Fieller CI and BEAST 95% HPD bands; (D) Alluvial lineage dynamic flow streamgraph and transverse manifold expansion ($W(t)$).
Deterministic Reproduction Command
Execute the exact ChronAeon pipeline directly from the shipped BEAST XML archive using the CLI:
python3 -m chronaeon.cli date \ --beast beast.xml.gz \ --loocv \ --nonlinear-clocks \ -o chronaeon_dating.json \ -c chronaeon_dating.csv