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Early Northern Hemisphere influenza surge and G155E mutation

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2026-10-22 11:45 UTC → 2026-10-24 05:21 UTC · added ~~removed~~

Public health officials in the Northern Hemisphere are reporting an unusually early onset of influenza activity. In the United States, the surge is notably driven by the West Coast rather than the South. Surveillance data from the United Kingdom and Japan also indicate higher-than-expected positive test rates. In Japan, outbreaks in August and early September resulted in the closure of some schools. Scientific concern has centered on the H1N1 subtype, which has accounted for approximately 96 percent of subtyped cases in some regions. Virologists at the University of Washington have identified an emerging G155E mutation, detected in 13 out of 17 H1N1 samples tested. This has raised concerns regarding the effectiveness of existing immunity. While the H3N2 strain was predominant last year, H1N1 is currently the primary subtype responsible for most cases in the United States. Recent laboratory findings suggest the G155E mutation may lead to reduced neutralization by antibodies, particularly in individuals aged 15 to 25 who may have limited prior exposure to this specific strain. Dr. Jennifer Duchon of Mount Sinai Hospital noted that the circulating H1N1 subtype could cause more severe illness in younger people due to this lack of immunity. While the mutation raises questions regarding antibody recognition, experts emphasize that current seasonal vaccines remain important for preventing complications. In La Réunion, the epidemic has persisted for five consecutive ~~weeks. Surveillance data indicates that~~ weeks, with 75 percent of emergency room visits for flu-like symptoms ~~involve~~ involving children and adolescents under ~~the age of~~ 15. Health authorities there have reported several severe cases, including six serious cases occurring within a single week, most of which involved unvaccinated individuals under the age of 65 with underlying risk factors. In the United States, the season ~~has begun~~ began approximately two and a half months earlier than typical years. In Washington state, ~~health officials report that recent~~ positivity rates have reached levels typically seen in January. Walgreens has noted that the national season is tracking about four weeks ahead of recent years, evidenced by an increase in the dispensing of antiviral prescriptions and cold medications. While the virus is spreading eastward across all regions, CDC data indicates that influenza-like illness visits remain below the national baseline.

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