A mutated strain of the H3N2 influenza virus, dubbed 'super flu,' is causing an increase in cases of vomiting bile among Britons, health experts have warned. The variant has undergone seven genetic mutations over the summer, making it more severe and leading to symptoms such as sudden fatigue, body aches, and vomiting on an empty stomach, which produces yellow bile.
Virologists explain that vomiting bile occurs due to inflammation of the stomach lining and reduced appetite, causing patients to vomit on an empty stomach. Professor Paul Hunter from the University of East Anglia noted that while this symptom is often associated with gastrointestinal viruses like norovirus, it can also occur with flu. Dr Simon Clarke of the University of Reading advised that staying hydrated is crucial, even if fluids are brought back up.
Hospital admissions for flu in England rose to 3.8 per 100,000 people in early November 2025, up from 2.4 the previous week, according to UK Health Security Agency (UKHSA) data. This level is typically seen in December, and flu rates remain over three times higher than normal for the time of year, with the highest rates among children and young people.
Health officials urge eligible individuals to get vaccinated against flu and COVID-19 to reduce the risk of severe illness. However, the current vaccine, designed in February, may not offer full protection against the mutant strain that emerged in June. Despite this, experts emphasise that vaccination remains vital to prevent severe outcomes.
Over the Christmas week, flu hospitalisations dropped to 2,676 from 3,061, aided by increased vaccination efforts. However, NHS National Medical Director Professor Meghana Pandit warned that the NHS is 'far from complacent' as freezing temperatures could increase pressures. Health Secretary Wes Streeting echoed these concerns, urging those eligible to come forward for jabs.
