Research and analysis

Situational assessment for SARS-CoV-2 variant V-23AUG-01 (BA.2.86)

Updated 1 September 2023

Applies to England

Part 1. Context and UK cases

As of 10am, 31 August 2023, 25 BA.2.86 genome sequences are available on the international genomic data-sharing platform, GISAID. These originate in 8 different countries:

• 10 in Denmark
• 4 in Sweden
• 4 in USA
• 2 in Portugal
• 2 in South Africa
• 1 in Canada
• 1 in Israel
• 1 in UK

Two further UK cases, one in England and one in Scotland, have been identified and genome sequence data will be available on GISAID shortly. This is a dynamic situation changing daily.

Sample dates, where known, range from 24 July 2023 (Denmark, South Africa) to 22 August 2023 (USA) (Figure 1).

The first UK case was reported in the previous risk assessment, published 18 August 2023. All UK cases were identified through hospital testing and have no known recent travel history through routinely collected data.

The first UK case was mildly unwell and the second UK case (England) did not have respiratory symptoms. The third UK case (Scotland) was symptomatic. The samples for the 2 new cases were sequenced through routine surveillance of hospital test-positive cases.

A number of additional countries have also made formal or informal announcements of BA.2.86 detection in wastewater. There is no internationally consistent repository for wastewater genomic data.

Figure 1. Epicurve of BA.2.86 genome sequences on GISAID, including additional 2 new UK cases

Figure 1 is a bar showing sequences grouped by week of sample collection (GISAID upload date is used where sample collection date is not available in one case). Total number of sequences per country are shown in the figure legend.

One sequence from both Denmark and USA, and 2 sequences from South Africa have collection dates available on GISAID from the week beginning 23 July 2023.

There was one sequence each from Denmark, Israel, and USA with a collection date from the week beginning 20 July 2023. One sequence from USA and Sweden, and 3 sequences from Denmark have a collection date in the week beginning 6 August 2023.

Three sequences from the UK, 3 from Sweden, 2 from Portugal and 4 from Denmark have a collection date from week beginning 14 August 2023.

One sequence from USA and one sequence from Denmark have a collection date from week beginning 20 August 2023. There was one sequence from Canada with a submission date from the week beginning 27 August 2023.

Part 2. Variant Technical Group assessment

Meeting and assessment 29 August 2023. The UK Health Security Agency (UKHSA) is aware of new data since this date and continues to assess all available information.

1. Through the limited available global genomic surveillance, the variant is present in multiple countries on multiple continents, detected at a low prevalence amongst clinical cases or in wastewater. Although an increasing number of countries are reporting detection, there is as yet no clear signal of growth within any of these individual countries.
2. The BA.2.86 phylogeny shows one sublineage within which most European cases are located but does not otherwise have a high degree of substructure. The time of most recent common ancestor (tMRCA) is estimated at 3 June (range 29 April, 1 July) assuming exponential growth.
3. BA.2.86 is an outlier in terms of geographic dispersion when compared to other nodes in the SARS-CoV-2 global phylogeny in 2023 with similar tMRCA and which are still circulating. However, it is not the most extreme outlier. This analysis does not incorporate countries detecting BA.2.86 through wastewater.
4. The group considered hypotheses of a mass gathering event seeding multiple countries, an ongoing outbreak in a country without surveillance, or widespread community transmission undetected by surveillance. All 3 possibilities were still considered plausible, though widespread high-level community transmission is not best supported by the phylogeny.
5. No conclusions can be drawn about the fitness of the variant based on this data, and a full range of options – from less fit than other circulating variants, to a large jump in fitness – are still possible, given the available data.
6. There is no laboratory data available. Two samples are in culture in the UK and we are also in contact with international partners. Neutralisation and other phenotypic data is still likely to be one to 2 weeks away at minimum in the UK.
7. The extant UKHSA variant of concern definition requires us to demonstrate (or confidently predict) a detrimental change in biological properties, as well as a growth rate compatible with displacement or maintenance. At present there are a wide range of possibilities for the fitness and growth of the variant and there remains uncertainty about the impact of the mutations present. BA.2.86 does not, therefore, meet this definition of a variant of concern. The Variant Technical Group discussed whether the current surveillance context required an updated approach to designating and acting on variants. However, any such updated definition of a variant of concern would include a higher level of confidence on positive growth than is available at present for BA.2.86.

Sources and acknowledgements

Variant Technical Group

Analysis submitted by:

• UKHSA Genomics Public Health Analysis Team
• UKHSA COVID vaccines and epidemiology team
• Public Health Scotland
• Andrew Rambaut
• Erik Volz

Members present for this assessment

• Meera Chand (chair)
• Susan Hopkins
• Wendy Barclay
• Fergus Cumming
• Daniela De Angelis
• Gavin Dabrera
• Susanna Dunachie
• John Edmunds
• Thomas Finnie
• Eileen Gallagher
• Natalie Groves
• Matt Holden
• Jamie Lopez-Bernal
• Kimberly Marsh
• Richard Myers
• Thomas Peacock
• Andrew Rambaut
• Gavin Screaton
• Emma Thomson
• Erik Volz
• Tom Ward