• A new Covid variant is currently circulating in a number of countries, including the UK.

Professor Tim Spector, founder of the Covid Zoe app, warned on 1 January that XBB.1.5 “could be the new variant to watch out for” this year.

So, what are the symptoms of the new variant and how many cases have been identified in the UK? Here’s what you need to know.

What are the symptoms of the new XBB.1.5 Covid variant?

XBB.1.5 is related to the Omicron variant of coronavirus that took hold at the end of 2021. This latest version was first spotted in India in August 2022.

Martin Michaelis, professor of molecular medicine at the University of Kent, told FactCheck “there is no indication” that the symptoms of XBB.1.5 differ from those caused by other Omicron sub variants.

The NHS says Omicron symptoms include a high temperature or shivering, a new, continuous cough, change to taste or smell, head and body aches, a sore throat, blocked or runny nose, tiredness and gastric symptoms.

How many cases of the variant has the UK had so far?

The XBB.1.5 sub variant makes up around 4 per cent of all UK cases, according to researchers at the Sanger Institute. This is the first time this version of Omicron has been named and listed on the Institute’s virus dashboard.

However, according to the UK Health Security Agency (UKHSA), XBB.1.5 is not currently a variant of concern in the UK. A variant is given the label if it has “significant characteristics” like being more easily spread, or causing more severe illness.

Addressing what XBB.1.5 could mean for the UK, Professor Lawrence Young, virologist at the University of Warwick, told Radio 4 on Wednesday (4 January) that “we do need to keep an eye on what’s going on in terms of the spread of this particular variant”.

He said more “genomic surveillance” – where different samples of the Covid virus are tested to see which variant is spreading the most quickly – needs to be carried out.

Does this Covid variant cause more severe illness than others?

Prof Michaelis told FactCheck the XBB sub variants of Covid “have not been clinically reported to cause more severe disease than previous Omicron sub variants.”

However, he said XBB and its sub variants, including XBB.1.5, are not well recognised by antibodies from Covid vaccines and previous infections with the virus. But Prof Michaelis added that “it is not yet clear what this means for the severity of the disease” that these sub variants cause.

This was echoed by Prof Young, who said there is “no evidence at this stage that this particular variant causes more severe disease.”

Is XBB.1.5 more easily spread than other variants?

Concern about XBB.1.5 is largely based on how it is spreading in the United States, where it now accounts for around 40 per cent of Covid cases in the country, according to data from the Centers for Disease Control and Prevention (CDC).

Prof Young said the new variant is “significant” because it is “spreading so rapidly”, with the number of Covid cases caused by XBB.1.5 more than doubling in a week in the US towards the end of December, leading scientists to be “very concerned”.

He noted there is “waning immunity” among the US population, with only 15 per cent of those eligible having received updated boosters, which is contributing to the variant being able to spread more rapidly.

A mutation named F486P is also thought to be helping the variant to spread easily. The mutation was highlighted on Twitter by Jesse Bloom, a computational virologist at the Fred Hutchinson Cancer Center in the US, who also said in an email to CNN that it is “clearly letting XBB.1.5 spread better”.

The mutation reduces the antibodies’ ability to neutralise Covid and allows the XBB.1.5 variant to spread.

Prof Young also highlighted this, as he said that XBB.1.5 is “more able to escape the protections of previous vaccinations and past infections” and that it is “very, very infectious” due to a “particular mutation that has arisen within this variant”.