COVID–19

Guidance for reporting on this website

The figures here are publicly available and will usually be updated each Monday at around 10am. However, it is not possible to directly embed these visualisations on third party websites. Caution should be exercised when drawing conclusions about variant incidence or trends based on these numbers alone. In particular, remember that:

It is not an official, validated output of the UK Health Security Agency

  • These are provisional data released by the Wellcome Sanger Institute for research purposes and for public interest. The UK Health Security Agency provides authoritative counts of variant sequences and detailed technical briefings on variants.
  • The Wellcome Sanger Institute generates genomic data on SARS CoV-2, which is provided to public health authorities to help inform decisions. We cannot comment on what these data mean for public health interventions, for example local lockdowns.

It is not a comprehensive record of SARS-CoV-2 incidence

  • The "Lineages (raw)" page displays lineages of SARS-CoV-2 in England that have been genome sequenced by the Wellcome Sanger Institute's COVID-19 Genomics Initiative.
  • Around 50 per cent of positive Covid Pillar 2 tests (community swab tests, not hospital tests) processed by Lighthouse Labs in England are sequenced each week.
  • Positive tests resulting from foreign travel or special studies are not included, where possible. This is to provide a more accurate representation of how widespread these variants are in the community. Prior to mid-April 2021 we also excluded “surge testing”, to avoid upwardly biased frequency estimates of rare variants of concern (e.g. B.1.351). However, excluding more recent surge testing would downwardly bias estimates of the increasingly common variant of concern B.1.617.2, so we have not excluded those samples.
  • These data are for England only, and our geographic coverage is not uniform. For example, few sequences were generated from the Southwest in April and early May.

Proportions of a particular variant are easy to misinterpret

  • A high proportion of variant cases could seem alarming if only the percentage is reported in areas with only a few sequences. If possible, also report the number of genomes per week to give a more accurate picture.
  • It is not recommended to report percentages in areas with fewer than ten genomes per week.

Accessing the data

Key terms

  • Genomes per Week – the average number of genomes that belong to a particular lineage per week over the two-week period ending on the specified date.
  • Proportion – the percentage of genomes sequenced in the selected two-week period that belong to a particular lineage.