UK health authorities have identified 77 cases of the highly infectious B.1.617 variant of coronavirus which causes COVID-19, first found in India, and has designated it a Variant Under Investigation (VUI).

Public Health England (PHE), which releases weekly updates on the number of confirmed new cases of Variants of Concern (VOC) and VUI in the UK, reported on Thursday that the variant first detected in India includes a number of mutations.

"A new variant has been designated a Variant Under Investigation (VUI) by PHE. The variant, first detected in India, includes a number of mutations including E484Q, L452R, and P681R," the PHE weekly report said.

PHE has identified 77 cases of this variant in the UK and all appropriate public health interventions will be undertaken, including enhanced contact tracing. This variant has been designated VUI-21APR-01. PHE and international partners continue to monitor the situation closely, it said.

The B.1.617 strain's mutations are feared to make the variant spread faster and partially evade immunity. The variant is believed to be largely responsible for India's current second wave of the COVID-19 pandemic, with infection rates and hospitalisations on the rise once again.

It also led to UK Prime Minister Boris Johnson deciding to shorten the length of his India visit later this month, with the bulk of the events now expected to be limited to a day-long packed schedule on April 26.

We have been in close contact with the Indian government about the Prime Minister's upcoming visit in light of the COVID-19 situation in India. As a result of these discussions the Prime Minister has made the decision to reduce the length of the visit, due to take place at the end of this month, to a shorter programme in New Delhi, the UK PM's spokesperson at 10 Downing Street said.

India at present is not on the "red list" of countries, which involves more stringent hotel-based quarantine requirements for travellers commuting between India and the UK. If further concerns emerge around the Indian B.1.617 variant in the UK, it could be categorised from a Variant Under Investigation to a Variant of Concern.

The latest addition brings the total number of variants detected in the UK to 56, including the so-called Kent variant and South African strains which is top of the UK's concerns. The PHE said that the dominant variant in the country continues to be VOC-20DEC-01 B.1.1.7, or the Kent variant, which is being monitored closely.

The best way to stop the spread of the virus is to remember: hands, face, space and follow the restrictions in place, the PHE said.

Earlier this week, people living in four boroughs in south London were urged to get tested as part of a surge testing drive after cases of the South African variant were found in Wandsworth, Lambeth, Barnet and Southwark.

It comes as all parts of the United Kingdom began easing lockdown restrictions gradually this week, with non-essential retail shops, hairdressers and outdoor-serving restaurants among the businesses allowed to operate once again after months of lockdown.