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The original India variant - officially known as B.1.617 - was first detected in the country in October.
That version has now been re-characterised as three different subtypes, all with slightly different genetic mutations.
The UK has seen a sharp increase in one version in particular, known as B.1.617.2, which now makes up the majority of all Indian variant cases and appears to be growing faster than other versions.
PHE scientists think with "moderate confidence" that it spreads at least as quickly as the version of the virus first found in Kent last year - known as B.1.1.7 - which is currently dominant in the UK.
But a source has told the BBC there is no evidence this version of the Indian variant is resistant to current vaccines.
It does not feature the E.484K mutation found in the South African variant of the virus, which could help the virus dodge a person's immune system and may affect how well coronavirus vaccines work.