New flu strain with rapid mutations causes early alarm

Early epidemiological data from the United Kingdom (UK) are causing concern among specialists as they record increasing circulation of the A(H3N2) K sub-type of influenza, which appears to show signs of greater transmissibility. The flu season started earlier than usual this year, with cases rising sharply in October, well ahead of the traditional start of activity, epidemiologists noted. The influenza virus constantly evolves, which is why the composition of the flu vaccine is adjusted every year. However, this particular variant appears to have accumulated an unusually large number of mutations in a short period. “This variant (the K) has evolved a bit faster, with more changes than we typically see,” Jamie Lopez Bernal, an epidemiologist at the UK Health Security Agency (UKHSA), told Time magazine. Greek and international monitoring begins In Greece, the President of the National Public Health Organisation (EODY), Christos Chatzichristodoulou, said that early UK data suggests the antigenically shifted K-clade of A(H3N2) is dominant in detections, which may indicate increased transmissibility. Greece’s National Flu Reference Centres for the South and North are checking for the possible circulation of this clade. The new strain, officially known as A(H3N2) K, has also been recorded in Japan, where health authorities recently declared an epidemic. Its mutations differentiate the strain from the one included in this year’s updated vaccines. Scientists in Canada are calling for close monitoring and more frequent genetic sequencing to assess the continued effectiveness of the vaccines. Despite these changes, preliminary data published by the UKHSA on 12 November shows that vaccination continues to provide strong protection against severe illness and the need for hospitalisation. Experts, however, stress that the level of protection shows a slight difference, at levels typically seen towards the end of the flu season when vaccine effectiveness naturally declines. Higher intensity flu season possible What this development could mean for this year’s season remains uncertain. “Influenza is notoriously unpredictable, so it’s very difficult to say what will happen,” Lopez Bernal said, adding that the simultaneous emergence of early activity and a worrying variant increases the likelihood of a more intense flu season. Dr Antonia Ho, an infectious disease specialist at the University of Glasgow, noted that early flu seasons usually lead to a higher number of people becoming ill, and seasons dominated by H3N2-type strains tend to affect the elderly more severely. In the United States, available data is limited, as a recent government shutdown delayed updates to the CDC surveillance system. The latest report from New York State, however, recorded a significant increase in cases, up 49% in one week, and a 71% rise in hospitalisations, although there is no evidence yet to indicate whether the K strain has reached the country.