Surge testing is taking place in locations across England to monitor and suppress the spread of new variants of the SARS-CoV-2 virus that causes Covid-19.

This Insight looks at what virus variants are, how they are assessed and what the Government is doing to curb the spread of ‘variants of concern’.

What is a virus variant?

All viruses constantly and naturally change through mutation. A mutation usually refers to a change that affects the nucleic acids in cells (the building blocks of DNA and RNA). A version of the virus with a collection of these mutations is called a ‘variant’.

Public Health England (PHE) notes that, over time, changes can “build up in the genetic code of the virus” and that, usually, these changes are so small that they have little impact on the virus and how it behaves.

There are occasions, however, where the virus mutates in a way that is beneficial to its ongoing survival. These sorts of mutations might, for example, mean that the variant is more transmissible (spreads more easily/faster) or that it makes people more ill. If a mutation benefits the virus, it may then out-compete other forms of the virus.

When does a variant become a ‘variant of concern’ (VOC)?

The assessment and analysis of new strains of the SARS-CoV-2 virus which causes Covid-19 is undertaken by PHE and its partners. The Covid-19 Genomics UK Consortium (COG-UK) provides large-scale, rapid whole-genome sequencing of SARS-CoV-2. COG-UK states that it aims to sequence around 10,000 positive samples each week based on its present capacity and that it aims to achieve “equity of sequencing and good coverage across the UK”. PHE’s New Variant Assessment Programme also works to support other countries to undertake genomic sequencing.

If a variant is found with concerning features (e.g, it appears to spread more easily or provokes a more severe infection), PHE explains that it begins a formal investigation:

At this point they [the variants] are designated Variant Under Investigation (VUI) with a year, month, and number. Following a risk assessment with the relevant expert committee, they may be designated Variant of Concern (VOC).

At the time of writing, there are five designated Variants of Concern and eight Variants under Investigation by PHE.

There is no agreed, international naming system for variants. The World Health Organization (WHO), however, has recently introduced a “simple” (non-scientific) approach to labelling variants, based on the Greek alphabet. Its aim is for the labelling system to be both “easy-to-pronounce and non-stigmatising”.

Surge testing to find and manage VOCs

Alongside laboratory testing of variants, PHE also works with local authorities to detect cases in the population to limit further spread. This is primarily achieved through ‘surge testing’ and contact tracing.

Surge testing aims to identify those who are asymptomatic or pre-symptomatic for Covid-19 (they are not showing any signs of having the disease) who may be unknowingly infected. It is typically conducted in areas where variants of the virus are known to be circulating so that self-isolation, and rapid finding and testing of close contacts, can interrupt community transmission. If a positive case is found, genomic sequencing of the test takes place.

Enhanced contact tracing is in place for people testing positive with a VOC. This aims to identify the locations the person may have acquired, or transmitted, the infection to conduct further Covid-19 testing.

Why is surge testing needed?

The Government explains that it is using surge testing and genomic sequencing to:

  • monitor and suppress the spread of Covid-19
  • better understand new variants

How does surge testing work?

Surge testing for Covid-19 began in England on 1 February 2021 and is limited to those areas where VOCs have been found. An up-to-date list of locations using surge testing can be found on the Gov.uk webpage, surge testing for new coronavirus (COVID-19) variants. This lists the postcode areas covered.

Everyone over the age of 16, living in the postcode areas listed, is strongly encouraged by the Government to take a Covid-19 PCR test. The programme is overseen by the local authorities (LAs) that are affected. LAs provide additional testing resources, such as delivering home testing kits, and/or through setting up mobile testing sites.

Surge vaccination

In response to the UK clusters of the Delta (B.1.617.2) variant, first observed in India, the Government has also put in place a form of ‘surge vaccination’ to accelerate vaccine take-up among eligible groups.

Two places with the highest number of cases of the B.1.617.2 variant are Bolton and Blackburn with Darwen. In both locations, the Government has set up new vaccination centres, as well as extending the hours and vaccination capacity at existing local sites. Provision has since been expanded to cover six further areas: Bedford, Burnley, Hounslow, Kirklees, Leicester and North Tyneside.

While there have been calls from public health experts to vaccinate all those aged over 18 years in areas with clusters of the variant, the Health Secretary has said the Government continues to follow advice set out by the Joint Committee on Vaccination and Immunisation (JCVI). He described this as:

first, prioritise anyone over 50 who has not yet been vaccinated; next, second doses to those over 50 are vital—that will now be done on a schedule of eight weeks; and, then, follow the cohorts in priority order, and the age groups as we open them. This clinically approved approach is the best way to save the most lives, rather than jumping ahead with first doses for younger people.

He explained that mobility data, and waste water monitoring, is being used alongside genomic data to help identify the spread of VOCs. The Government has also implemented international travel restrictions (and in some instances, travel bans) to help reduce the risk of new VOCs entering the country, though there has been criticism of the speed at which countries have been added to the red, ‘travel ban’ list. 

Where is data on variant case numbers available?

PHE publishes ‘technical briefings’ on SARS-CoV-2 variants of concern and variants under investigation in England. These cover variant prevalence, growth rates, cases of reinfection as well as providing breakdowns of the number of cases of different variants by regions.

The Wellcome Sanger Institute publishes its Covid-19 Genomic Surveillance data on variants by local authority area.

Further reading

About the author: Elizabeth Rough is a medical and health specialist at the House of Commons Library.

Image by Tim Dennell, under CC BY-NC 2.0, cropped

Note: This Insight was updated on 1/6/2021 to reflect the WHO’s new guidance on naming variants.

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