UK Health Security Agency (UKHSA) bosses have raised the alarm about the new variant called Eris which is up in the UK, and experts have said it could have spread through people heading to the cinema to see the popular films.
Professor Lawrence Young, a virologist at Warwick University, told MailOnline that "increased cinema attendance" as well as "more indoor mixing" due to bad weather may have contributed towards a rise in cases.
He said: "The EG.5.1 variant does appear to be spreading more efficiently in various Asian countries and is accounting for more infections in the UK.
"There is no evidence that this variant is more dangerous in causing severe disease.
"The rise in cases in the UK is probably due to waning protective immunity — it's some time since people received their last booster jabs and/or were previously infected — and to increased mixing in enclosed, poorly ventilated spaces.
"Poor weather over the last month has meant more indoor mixing including during various events such as university degree congregations and increased cinema attendance."
He added: "Overall levels of infection remain low but this is a wake up call stressing that we can't be complacent when it comes to Covid.
"We need to keep an eye on the emergence of variants and be vigilant as we prepare for an inevitable increase in infections over the autumn/winter."
UKHSA analysts estimate Covid positivity rates increased 5.4 per cent on the previous week, which itself saw a rise of 3.7 per cent.
Eris now makes up one in seven new cases after reaching the UK towards the end of May.
But experts say it shows no sign of being more dangerous than the other strains circulating.
Dr Simon Clarke, a microbiologist at Reading University, told the publication: "Covid will continue to change and adapt.
"So we shouldn't be shocked or worried just because new variants appear and cause increasing numbers of infections.
"The protection against serious illness provided by vaccination is still holding up well and while numbers of infections go up and down, hospitalisations and deaths remain reassuringly low."
He added:"There's no reason to be complacent.
"But unless people are again admitted to hospital in large numbers and struggling to breathe, people should live their lives as normal."
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