Health experts have been warned of an extremely transmissible variant of coronavirus which is sweeping across the globe at a "fast pace".
Experts are concerned with some symptoms associated with the strain which could bring back mask-wearing in the UK.
It is believed that the XBB.1.16, also known as Arcturus, has spread into at least 33 countries, with the United States recording between 12 and 14 per cent of their cases in country to the strain - and the numbers are continuing to rise.
Symptoms for the new subvariant include a general feeling of unhappiness (malaise), conjunctivitis, cough and fever.
Health officials in India have been put on alert, where the variant is believed to have derived from, and have already returned to mask-wearing requirements as the country tries to tackle the latest strain.
Dr Javeed Siddiqui, an infectious disease specialist who is also the co-founder and chief medical officer at TelMed2U, told the Express: "The one thing that we understand about SARS coronavirus is that there is no predicting this virus.
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"We are well aware, but this virus continues to mutate and develop new variants. We now have a variant that is increasing across 33 countries, including the United States at a fast pace."
He added: "Several research laboratories indicated that this variant is up to 1.2x more transmissible than its predecessor XBB.1.5."
The Californian-based expert also insists that both the US and the UK should resort to wearing masks on transport and in large gatherings, particularly the vulnerable, in a bid to reduce infection.
The outlet has reported that UK experts have recommended the use of facial coverings following five deaths associated with the XBB.1.16 variant.
Dr Siddiqui said: "Clinical data indicates that vaccinated individuals tend to have a reduced duration and intensity of infection.
"If you have not yet received the bivalent Covid booster dose, I urge you to do so as soon as possible.
"Masking, social distancing, and vaccination really do work, and are among the best tools to reduce your risk of infection."
The XBB.1.16 strain was first reported in January 2023. On April 17, the World Health Organization (WHO) designated it a Variant of Interest.
As of last month, there were at least 135 cases in the UK - a figure that may have risen since.
It was present in all corners of the UK apart from the North East, with the highest concentration of cases present in London, the North West and South East.
