“Now is not the time” to relax requirements for face masks to be worn in schools as a newer strain of the virus from India is named a “variant of concern” by Public Health England, teachers have warned.

There were originally four variants of concern in the UK - the Kent, South Africa, Brazil and Bristol variants.

But now a newer strain from India has been declared a new variant of concern by Public Health England amid rising cases.

It is thought there have been at least 48 clusters of the B.1.617.2 variant, with cases reported in secondary schools, care homes and places of worship.

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Towards the end of April, further testing was carried out at a Leicester school after three cases of the new Indian Covid-19 variant were found.

The cases were linked to travel from India from before the country was put on the government’s ‘red list’ meaning that travellers now have to go into hotel quarantine on their return.

Cases of the variant have also been reported in the North West - predominantly Bolton - and in London.

Teachers and unions are worried that reports that the prime minister is set to announce a lifting of the rule on face masks being mandatory in schools on Monday will come too soon when it is still important to do all that can be done to prevent the spread of coronavirus.

Reena Upadhyaya, 32, a secondary school teacher in Leicester, told Tes she would be concerned if the rules were lifted to stop face masks being mandatory in schools, particularly as she is pregnant.

“Luckily, the school where I work has not had any coronavirus cases for a few months.” she said.

“But students can choose to wear masks in lessons and around 80 per cent of them do and teachers and pupils wear masks in the corridors.

“For me, there is the added risk as a pregnant teacher in a school and I would be concerned if the government said that masks no longer need to be compulsory in schools.”

The English teacher added there was an extra worry about the Indian variant as Leicester has a high ethnic minority population.

“Leicester has been one of the worst affected areas for coronavirus and with this new Indian variant becoming a concern, I feel now is not the time to lift restrictions on face masks in school,” she said.

Kevin Courtney, joint general secretary of the NEU teaching union, said the sharp increase in the prevalence of the Indian variant of the virus shows how quickly the situation can change.

“This is the radically uncertain nature of Covid-19.” he said.

“The data in this country is going fantastically well, but there has to be a concern that one of these variants might unsettle that.

“We have to keep on top of that with testing and restrictions on travel to stop it coming into the country.”

He added that although coronavirus cases in schools were now very low, precautions needed to be taken to avoid the huge disruptions that occurred in the autumn.

“Keeping cases down in schools is really important so that we don’t go back to when large numbers of children were going home to self isolate.

“This is one of the reasons we wrote to the government together with other unions and scientists to ask for mask wearing measures to be kept for longer to stop cases rising.

“The concern is that with the opening up of other places on May 17 and if we get a variant taking hold, the cases will rise again.

“This is why we felt mask wearing should continue and it adds to the advice we gave to the government that now is not the time to ease mask wearing in schools.”

Geoff Barton, general secretary of the Association of School and College Leaders, said: “In the event of any cases of the variant Covid strain first identified in India, we would envisage that Public Health England will be advising schools on the next steps to take.

“Clearly, this strain is of concern but schools have in place very effective protocols to minimise the risk of virus transmission.

“We are expecting an announcement on the future use of face masks imminently and this decision must be based upon scientific advice that takes into account all circumstances, including the prevalence of this new variant strain of the virus.”