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This repository analyzes viral genomes using Nextstrain to understand how SARS-CoV-2, the virus that is responsible for the COVID-19 pandemic, evolves and spreads.

We maintain a number of publicly-available builds, visible at

See our change log for details about backwards-incompatible or breaking changes to the workflow.


Use Nextstrain to analyze your SARS-CoV-2 data

We’ve written a comprehensive guide to get you up and running in <1 hr. Click on the below links to follow it. It covers:

  1. Introduction (Start here)
  2. Setup and installation
  3. Preparing your data
  4. Orientation: analysis workflow
  5. Orientation: which files should I touch?
  6. Running & troubleshooting
  7. Customizing your analysis (see also: reference for all configuration parameters)
  8. Customizing your visualization
  9. Options for visualizing and sharing results (including working with sensitive metadata)
  10. Interpreting your results
  11. Writing a narrative to highlight key findings
  12. Running the pipeline starting with multiple inputs

Reference guides

Download formatted datasets

The hCoV-19 / SARS-CoV-2 genomes were generously shared via GISAID. We gratefully acknowledge the Authors, Originating and Submitting laboratories of the genetic sequence and metadata made available through GISAID on which this research is based.

In order to download the GISAID data to run the analysis yourself, please see this guide.

Please note that data/metadata.tsv is no longer included as part of this repo. However, we provide continually-updated, pre-formatted metadata & fasta files for download through GISAID.

Read previous Situation Reports

We issued weekly Situation Reports for the first ~5 months of the pandemic. You can find the Reports and their translations here.


  • Can’t find your sequences in Nextstrain? Check here for common reasons why your sequences may not be appearing.
    You can also use to perform some basic quality control on your sequences. If they are flagged by this tool, they will likely be excluded by our pipeline.
  • For information about how clades are defined, and the currently named clades, please see here. To assign clades to your own sequences, you can use our clade assignment tool at

Bioinformatics notes

Site numbering and genome structure uses Wuhan-Hu-1/2019 as reference. The phylogeny is rooted relative to early samples from Wuhan. Temporal resolution assumes a nucleotide substitution rate of 8 × 10^-4 subs per site per year. There were SNPs present in the nCoV samples in the first and last few bases of the alignment that were masked as likely sequencing artifacts.


We welcome contributions from the community! Please note that we strictly adhere to the Contributor Covenant Code of Conduct.

Contributing to software or documentation

Please see our Contributor Guide to get started!

Contributing data

Please note that we automatically pick up any SARS-CoV-2 data that is submitted to GISAID.

If you’re a lab and you’d like to get started sequencing, please see:

Get in touch

To report a bug, error, or feature request, please open an isssue.

For questions, head over to the discussion board; we’re happy to help!


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