Doctors are carefully monitoring a new strain of the virus which causes Covid - and have put together a comprehensive list of symptoms. There is concern for the NB.1.8.1 strain of Covid, officially designated a "variant under monitoring" by the World Health Organisation (WHO) due to its rapid rise. Seven people in Northern Ireland have been diagnosed with the strain , which has the potential to evade immunity from previous infections or vaccines. Some symptoms are the same as ones associated with previous strains, however medics have confirmed new signs - like heartburn - have been noted too. Gastrointestinal symptoms can include abdominal pain and bloating, doctors added. NB.1.8.1 already the dominant strain in Hong Kong and China , and has been detected in Australia , the US and across popular holiday destinations including Egypt, Thailand and the Maldives. The full list of symptoms are; According to WHO data, the strain has jumped from 2.5% to 10.7% of submitted global sequences in just four weeks, which has prompted growing international concern. A WHO spokesperson said: "SARS-CoV-2 continues to evolve, and between January and May 2025, there were shifts in global SARS-CoV-2 variant dynamics. At the beginning of the year, the most prevalent variant tracked by WHO at the global level was XEC, followed by KP.3.1.1. "In February, circulation of XEC began to decline while that of LP.8.1 increased, with the latter becoming the most detected variant in mid-March. Since mid-April, the circulation of LP.8.1 has been slightly declining as NB.1.8.1 is increasingly being detected." Experts say NB.1.8.1 carries multiple mutations that "may infect cells more efficiently than earlier strains". Dr Lara Herrero explained: "It's possible a person infected with NB.1.8.1 may be more likely to pass the virus on to someone else, compared to earlier variants. The evidence so far suggests NB.1.8.1 may spread more easily and may partially sidestep immunity from prior infections or vaccination. These factors could explain its rise in sequencing data. "But importantly, the WHO has not yet observed any evidence it causes more severe disease compared to other variants. Reports suggest symptoms of NB.1.8.1 should align closely with other Omicron subvariants."