Nextstrain build for novel coronavirus SARS-CoV-2
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Change Log

As of April 2021, we use major version numbers (e.g. v2) to reflect backward incompatible changes to the workflow that likely require you to update your Nextstrain installation. We also use this change log to document new features that maintain backward compatibility, indicating these features by the date they were added.

New features since last version update

v10 (5 January 2022)

  • 5 January 2022: Move filter and diagnostic steps after subsampling. For workflows with subsampling that does not depend on priority calculations, these changes allow the workflow to start subsampling from the metadata, skipping sequence alignment of the full input sequences and only looping through these input sequences once per build when subsampled sequences are extracted. To skip the alignment step, define your input sequences with the aligned directive. If you use priority-based subsampling, define your input sequences with the sequences directive. This reorganization of the workflow causes a breaking change in that the workflow no longer supports input-specific filtering with the exclude_where, min_date, and exclude_ambiguous_dates_by parameters. The workflow continues to support input-specific filtering by min_length and skipping of diagnostic filters with skip_diagnostics. PR #814.

  • 20 December 2021: Surface the crowding penalty parameter via the config file: PR #828, Issue #708. The crowding penalty, used when calculating priority scores during subsampling, decreases the number of identical samples that are included in the tree during random subsampling to provide a broader picture of the viral diversity in your dataset. However, you may wish to set crowding_penalty = 0.0 (default value = 0.1) if you are interested in seeing as many samples as possible that are closely related to your focal set. You can change this parameter via config['priorities']['crowding_penalty']. There is no change to default behavior.

  • 7 October 2021: Automatically exclude sequences whose dates are more than two weeks (this parameter can be adjusted) before the first known sequences for their corresponding clade: PR #740. To be extended to provide a tsv of all auto-excluded sequences and reasons for exclusion such as the reason addressed in the afformentioned PR, AKA check_clade_dates, and others checked in scripts/

  • 6 October 2021: Add three configuration parameters to control the metadata sanitizer step of the workflow. These parameters allow users to specify the metadata columns to use for strain names (metadata_id_columns) and to resolve duplicate records with database ids (database_id_columns). The new error_on_duplicate_strains parameter allows users to ask the workflow to exit with an error when any duplicates appear in the metadata. See the configuration reference for more details. (#728)

  • 6 October 2021: Update clades with 21I (Delta) and 21J (Delta) viruses. These are subclades within 21A (Delta). Based on mutations they should have largely Delta-like phenotypes, although additional ORF1a mutations in 21J (Delta) appear to confer higher fitness.

v9 (6 October 2021)

  • 6 October 2021: Remove travel exposure adjustment. This is a potentially breaking change if you had explicitly opted into this functionality (by default, it was disabled); in this case your snakefile will print an appropriate error and exit. Note that you can still define exposure metadata traits as colorings in your auspice-config.json, however be aware that these may not be curated in the future. See PR 723 for more.

  • 6 October 2021: Change how the internal (core) nextstrain profiles are run. We now split each (GISAID, open) into a preprocessing profile and a phylogenetic build pipeline. Please see PR 730 for more. There should be no changes to other profiles.

  • 19 September 2021: Include “mutational fitness” coloring based on Obermeyer et al model. This annotates each node in the tree with a mutational_fitness trait by summing mutational effects from Obermeyer et al Supplementary Data S2. This should provide a mechanism to flag emergence of novel variants that may have higher fitness than circulating viruses.

v8 (19 Aug 2021)

Major changes

  • Annotate CDC-style epiweeks (e.g., “202019”) as a color-by and filter option in Auspice JSONs (#703). This functionality requires the Python epiweeks package. You will need to update your software environment to include this package, depending on how you run your builds.
    • If you use the Nextstrain CLI with Docker, update the Docker image with nextstrain update and then run your builds as usual with nextstrain build.
    • If you use the Nextstrain CLI without Docker, run your builds with nextstrain build . --use-conda <...other options...>.
    • If you use Snakemake, run your builds with snakemake --use-conda <...other options...>.
    • If you manage your own Conda environment, install epiweeks manually in the environment with conda install -c bioconda epiweeks.


  • Update Conda environment to use Augur 13.0.0 for an improved filtering experience (#703).

New features since last version update

  • 11 August 2021: Add support for “Sequences” and “Patient status metadata” downloads from GISAID’s search interface including documentation in the tutorial of how to use these data. (#701)
  • 6 August 2021: We’ve replaced the mechanisms that support remote file inputs (e.g. s3:// URLs) to improve internal workflow structure, extend support to gs://, http://, and https:// URLs, and expand support for compressed inputs. Our remote file inputs documentation is updated to reflect the changes.

    This change should be backwards compatible and largely transparent to end users. The most visible change for anyone using remote file inputs is the local download location of the remote files: instead of being within the results/ directory, dynamic directories based on the remote URL are now used. For example, the remote metadata input would be downloaded to the local path; the remote sequences input s3://nextstrain-data/files/ncov/open/sequences.fasta.xz would be downloaded to nextstrain-data/files/ncov/open/sequences.fasta.xz.

  • 7 July 2021: Extensive changes to internally-used Nextstrain profiles. There should be no breaking changes to existing workflows outside of ./nextstrain_profiles/. Please see PR #628 for full details. Briefly:
    • The (GISAID) profile has been renamed to ./nextstrain_profiles/nextstrain-gisaid
    • A new “open” (GenBank) profile has been added ./nextstrain_profiles/nextstrain-open
    • Intermediate open (GenBank) files, including sequences, & alignments are now publicly available for workflows to use as starting points. See the remote inputs documentation for details.
  • 3 July 2021: Allow optional prefixing of hCoV-19/ to strain names when exporting Auspice JSON for visualization. This is specified via the config option include_hcov19_prefix. This is included in Nextstrain-maintained builds at the request of GISAID.
  • 27 June 2021: Update clade definitions with 21G (Lambda, C.37) emerging from Peru and 21H (B.1.621) emerging from Colombia.
  • 22 June 2021: Add the ability to specify subsampling via a priorities.tsv file. To use, set the priorities > type: file and add priorities > file: path/to/priorities.tsv to your build’s subsampling schema. priorities.tsv contains strain name\tarbitrary numerical value. Higher values = higher priority. (#664)
  • 18 June 2021: Change default behavior of frequency estimation to estimate frequencies starting 1 year prior to the current date. To override this default behavior, define a min_date in the frequencies section of the builds configuration. (#659)

v7 (27 May 2021)

For more details about this release, see the configuration reference for the new “sanitize metadata” parameters and the corresponding pull request.

Major changes

  • Deduplicate metadata and sequences from each inputs dataset at the beginning of the workflow.


  • Support full GISAID metadata and sequences from the “Download packages” interface by converting this default format into Nextstrain-compatible metadata and sequences.
  • Support reading metadata and sequences directly from GISAID’s tar archives. For example, you can now define inputs as metadata: data/ncov_north-america.tar.gz and sequences: data/ncov_north-america.tar.gz to decompress and read the corresponding data from the archive.

New features since last version update

v6 (20 May 2021)

Major changes

  • Fix bug in precedence of input data such that duplicate sequence and metadata records are resolved by always preferring the record from the last inputs dataset. Thank you to @ttung for catching/patching this! If you have depended on the previous behavior where the sequence from first input dataset was preferred, you will need to change the order of your inputs such that the preferred input appears last in the list. (#639).

New features since last version update

  • 19 May 2021: Compress metadata, sequence indices, and early intermediate sequences (aligned, masked, filtered, combined for subsampling, and subsampled files) to save disk space. (#636)
  • 12 May 2021: Include S1 mutations and nextalign-based ancestral amino acid mutations in Auspice JSONs by default instead of requiring the now-unnecessary use_nextalign configuration parameter. (#630)
  • 12 May 2021: Document all available workflow configuration parameters. (#633)

v5 (7 May 2021)

See the corresponding pull request for more details about this release.

Major changes

  • Drop support for old sequence/metadata inputs. This change removes support for the config["sequences"] and config["metadata"] starting points for the workflow in favor of the more flexible config["inputs"] format.
  • Use nextalign for alignment instead of mafft. This change completely removes support for mafft in favor of nextalign. Future versions may reinstate mafft support as part of augur align updates.

Minor changes

  • Drop unused haplotype status rule and script
  • Remove unused nucleotide mutation frequencies rule
  • Use augur distance for mutation counts instead of a custom script in the ncov repository. Recent improvements to augur distance in v12.0.0 enable this change by properly accounting for insertion/deletion events.

v4 (5 May 2021)

See the corresponding pull request for more details about changes in this release.

Major changes

  • Change the default build name from “global” to “default-build” and use a default subsampling scheme that selects all input sequences
  • Warn about duplicate sequences found when merging sequences from multiple inputs instead of throwing an error (set combine_sequences_for_subsampling: warn_about_duplicates: false in your configuration file to revert this behavior)


  • Define a new subsampling scheme named all that selects all input sequences
  • Add a new top-level configuration parameter default_build_name to allow overriding new default name of “default-build”
  • Support compressed sequence inputs for alignment with mafft and nextalign (requires mafft upgrade)
  • Sanitize strain names in sequences and metadata from different sources (e.g., hCoV-19/ from GISAID or SARS-CoV-2/ from GenBank, etc.)

New features since last version update

  • 20 April 2021: Surface emerging lineage as a colorby. This replaces the rather stale color by “Emerging Clade” with a new color by “Emerging Lineage”. This focuses on PANGO lineages that are of interest triangulated by CoVariants, PANGO international lineage reports, CDC VUIs and VOCs and PHE VUIs and VOCs. The intention is for the listing at emerging_lineages.tsv to be updated frequently with new lineages added and no longer interesting lineages dropped. #609

  • 12 April 2021: Calculate current clade frequency and logistic growth rate across nodes in the phylogeny. This produces a new logistic_growth.json file and uses this file to add a coloring the final Auspice JSON. Implementation choices are discussed in PR #595.

  • 12 April 2021: Annotate Pangolin lineages per build in a pangolineages.json file and final Auspice JSON by adding run_pangolin: true to the top-level workflow config (builds.yaml). Note: this annotation only works when running the workflow with Snakemake’s --use-conda flag or if your environment has Pangolin installed. #593

v3 (12 April 2021)

  • Use Augur 11.2.0’s metadata-only output arguments to aggregate subsampled sequences and metadata #592
  • Use Augur 11.3.0’s module to combine and deduplicate uncompressed or compressed sequences when handling multiple input datasets #592

v2 (9 April 2021)

This release reflects the state of the workflow when we instituted our workflow versioning system.

July 2020 Update

In order to make our repository more accessible for first-time users, and those who want to create their own customized build, we made a number of changes in July 2020. Here, we outline those changes, and also list ‘breaking changes’ that may effect advanced users who were already running their own builds.

You can check the lists below to see if there’s any action you could take to make updating to the latest version of this repository is smooth!

Summary of changes

The goal of this release is to make it easier for new users to get their own ncov build up and running. This consists of a new, extensive tutorial hosted on github pages; a simplified repository structure; and more didactic file names.

Summary of breaking changes:

  • All nextstrain-specific files now live under nextstrain_profiles
  • config is now named defaults
  • envs, rules and schemas now live under workflow

Additions and updates

  • README is updated
  • Adds in-depth tutorial to docs/ and accompanying github pages setup files
  • data/ now contains example data that should remain packaged with the repository
  • narratives/ now contains only a for new users (not to worry – all finished Situation Reports are still hosted over in the nextstrain/narratives repo)
  • my_profiles now contains extensive example (formerly king-county) and example_advanced_customization (formerly swiss) profiles

File name changes

  • The main config.yaml file is now more precisely labeled as parameters.yaml
  • >
  • ordering.tsv > color_ordering.tsv
  • config > defaults, with nextstrain-specific files (e.g., moved to nextstrain_profiles/nextstrain/
  • nextstrain-specific profiles labeled with nextstrain_*

Structural changes

To improve repo clarity and approachability for new users, the following files have been reorganized.

  • Workflow-related files now live in a workflow directory, rather than the top level
    • envs > workflow/envs
    • schemas > workflow/schemas
    • rules > workflow/snakemake_rules
  • Nextstrain-specific profiles now live under nextstrain_profiles

(Reiterated from last section because they’re important :)

  • config is now defaults, with nextstrain-specific files (e.g., moved to nextstrain_profiles/nextstrain/
  • config.yaml is now parameters.yaml

Breaking Changes

If you’ve got custom builds running and regularly pull from the repository, you should check here to see if any of the changes you’ve made might make the merge harder. Usually, just copying and renaming folders and/or files is enough to avoid too many merge conflicts!

First, you should check the file locations that have changed, above. If you reference any of these files specifically in your pipelines or profile, be sure to update those links!

Be sure to also check any links to files that were previously in profiles. For example, if you were referencing the cluster information in profiles/nextstrain-scicore/cluster.json for example) - we’ve now got two profiles folders - you’d find nextstrain-scicore in the nextstrain_profiles folder now.

If you modified the swiss, default, or king-county profiles, this may cause a merge conflict, as these folders have been renamed. To keep your builds as they are, we recommend copying these folders, and then after the merge, restoring the name you prefer.

We now have a data folder which comes with the repository and contains example build data. If you had previously created a data folder, this may cause a merge conflict - usually this can be easily resolved.

Developer Changes

For those who help run and maintain the builds, there’s a few changes that might be different from what you’re used to.

Just focusing on the files mostly accessed by the ‘build shepherds,’ here’s what’s good to know:

  • The config folder is now defaults
  • orderings.tsv is now color_orderings.tsv
  • rules/nextstrain_exports.smk (the rules that do the ‘finalizing’ of the builds) isnow workflow/snakemake_rules/export_for_nextstrain.smk

The ‘finishing builds’ commands are also slightly different because the profiles have moved - they’ll look familiar though! You can already find these changed commands in the export_for_nextstrain.smk file, but here they are as well:

# To update ordering/lat_longs after AWS download:
#   snakemake --touch --forceall --profile nextstrain_profiles/nextstrain
#   snakemake --profile nextstrain_profiles/nextstrain clean_export_regions
#   snakemake --profile nextstrain_profiles/nextstrain export_all_regions
# When done adjusting lat-longs & orders, remember to run
#   snakemake --profile nextstrain_profiles/nextstrain all_regions
# to produce the final Auspice files!