Experts say this variant, named Delta by the World Health Organization, is more transmissible than even the “Kent” or Alpha variant and is now dominant in the UK.
It could delay the final stage of easing of England’s Covid restrictions on 21 June, although hospitalisations remain flat.
What is happening with the India variant in the UK?
There are a few “India” variants, but one called B.1.617.2 appears to be spreading more quickly in the UK.
Surge testing is being deployed in some areas, including Bolton and Blackburn, to identify infections – but it may not be stopping the spread.
Second jabs for all over-50s (and the clinically vulnerable) in England are now being brought forward to protect more people, faster. Second doses will come eight weeks after the first, rather than 11-12 weeks.
Latest research suggests the Pfizer and AstraZeneca coronavirus vaccines are highly effective against the variant after two doses, but protection from one dose appears to be reduced.
What do we know about the different variants?
There are thousands of different variants of Covid circulating across the world.
Viruses mutate all the time and most changes are inconsequential. Some even harm the virus. But others can make the disease more infectious or threatening – and these mutations tend to dominate.
Those with the most potentially concerning changes are called “variants of concern” and kept under the closest watch by health officials, and include:
- The India or Delta variant (B.1.617.2) of which more than 75,000 cases have been seen in across the UK
- The UK, Kent or Alpha variant (also known as B.1.1.7) is prevalent in Britain – with more than 200,000 cases identified – and has spread to more than 50 countries and appears to be mutating again
- The South Africa or Beta variant (B.1.351) has been identified in at least 20 other countries, including the UK
- The Brazil or Gamma variant (P.1) has spread to more than 10 other countries, including the UK
Are they more dangerous?
There is no evidence that any of them cause much more serious illness for the vast majority of people.
As with the original version, the risk remains highest for people who are elderly or have significant underlying health conditions.
But a virus being more infectious and equally dangerous will in itself lead to more deaths in an unvaccinated population.
The advice to avoid infection remains the same for all strains: wash your hands, keep your distance, wear a face covering and be vigilant about ventilation.
How are the mutants behaving?
The variants experts concerned about have all undergone changes to their spike protein – the part of the virus which attaches to human cells.
The Delta variant has some potentially important ones (such as L452R) that might make it spread more easily.
There is no evidence to indicate it causes more severe disease or might make current vaccines less effective, say UK officials.
The World Health Organization, meanwhile, has classified another, similar variant that is also circulating in India – called B.1.617 – as a variant of concern.
One mutation, called N501Y, shared by the Alpha, Gamma and Beta variant seems to make the virus better at infecting cells and spreading.
The Beta and Gamma variants also have a key mutation, called E484K, that may help the virus evade antibodies, key parts of the immune system which help bodies fight off infection.
Experts recently found a small number of cases of the Alpha variant that have this change too.
Will vaccines still work against variants?
Current vaccines were designed for earlier versions of coronavirus, but scientists believe they should work, albeit potentially less well.
Lab research suggests antibodies that can fight the infection – triggered by vaccination or past infection – may be somewhat less effective against Delta.
Two doses of either the Pfizer or AstraZeneca vaccine still protect people from getting very ill, however.
One recent study suggests the Gamma variant may resist antibodies in people who’ve recovered from Covid before.
Some early results suggest the Moderna vaccine is effective against the Beta variant, although the immune response triggered may be weaker and shorter-lived.
Do variants mean booster jabs are more likely?
Experts are confident existing vaccines can be redesigned to better tackle emerging mutations.
The UK government has a deal with biopharmaceutical company CureVac to develop vaccines against future variants, and has pre-ordered 50 million doses.
Depending on how variants continue to develop, these could potentially be used to offer a booster vaccine to older or clinically vulnerable people later in the year.