ETIDIOH - NEW

  February 2026  WHO convenes technical consultations {1} in February and September each year to recommend viruses for inclusion in influenza vaccines {2} for the northern hemisphere (NH) and southern hemisphere (SH) influenza seasons, respectively.  This recommendation relates to the influenza vaccines for use in the NH 2026-2027 influenza season .  A recommendation will be made in September 2026 relating to vaccines that will be used for the SH 2027 influenza season.  WHO guidance for choosing between the NH and SH formulations for countries in tropical and subtropical regions is available on the WHO Global Influenza Programme website {3}.   National or regional authorities approve the composition and formulation of influenza vaccines used in each country.  National public health authorities are responsible for making recommendations regarding the use of the vaccine.  WHO has published recommendations on the prevention of influenza {4}....

  Abstract As part of its role in the World Health Organization (WHO) Global Influenza Surveillance and Response System (GISRS), the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne received 12,180 human influenza-positive samples during 2024 . Viruses were analysed for their antigenic, genetic, and antiviral susceptibility properties . Selected viruses were propagated in qualified cells or embryonated hens’ eggs for potential use in seasonal influenza virus vaccines. During 2024 , influenza A( H1N1 )pdm09 and A( H3N2 ) viruses predominated , accounting for 33% and 42%, respectively, of all viruses received, compared to 5% for influenza B/Victoria . Of note, one influenza A(H5N1) virus was also received in 2024 . The majority of A(H1N1)pdm09 (98%), A(H3N2) (88%) and influenza B (100%) viruses analysed at the Centre were found to be antigenically and genetically similar to the respective WHO recommended vaccine strains for the Southern Hemisphere in 2024...

  Abstract Influenza B viruses cause substantial respiratory disease and seasonal outbreaks. Despite decades of circulation in humans , only the B/Victoria lineage persisted after the COVID-19 pandemic. Continual evolution has generated hemagglutinin deletion variants at residues 162-164 that drive successive epidemics , yet their functional consequences remain poorly understood. Using integrated phylodynamics and reverse genetics , we show that Clade V1A.1 viruses carrying a two-amino acid deletion exhibit enhanced replication and increased virulence compared with ancestral viruses lacking deletions. The recently prevailing Clade V1A.3 , which harbors a three-amino acid deletion together with the K136E substitution, has completely displaced V1A.1 and causes more severe disease in mice . Both clades bound efficiently to alpha 2-3 and 2-6 sialylated glycans and exhibited broad tolerance to acidic pH and elevated temperatures . These findings reveal that specific combinations of HA d...

  Abstract We characterized influenza A(H1N1)pdm09, A(H3N2), and B/Victoria viruses circulating in Japan during 2023–2024 , focusing on lineage placement relative to WHO-recommended vaccine strains and on baloxavir resistance (PA/I38T substitutions). We enrolled 210 outpatients with influenza-like illness across eight clinics in six prefectures (October 2023–September 2024). Of these, 209 had an analyzable pre-treatment respiratory specimen for RT-PCR; hemagglutinin (HA) and neuraminidase (NA) genes were sequenced by next-generation sequencing (NGS). PA/I38T substitutions that confer baloxavir resistance were assessed by cycling-probe RT-PCR, Sanger sequencing, and NGS. HA phylogenies were constructed with global datasets and WHO vaccine reference strains. Of 209 pre-treatment specimens, 181 were influenza-positive (A(H1N1)pdm09 44.2%, A(H3N2) 37.6%, B/Victoria 18.2%); 51 follow-up specimens were collected ≈4–5 days after baloxavir or neuraminidase inhibitor therapy . HA phylogeny ...

  10 December 2025 Situation at a glance Seasonal influenza (‘the flu’) is an acute respiratory infection caused by influenza viruses that circulate globally and year-round.  It can cause illness ranging from mild to severe , sometimes resulting in hospitalization or death.  Seasonal influenza activity has increased globally in recent months, with an increased proportion of seasonal influenza A(H3N2) viruses being detected.  This rise coincides with the onset of winter in the northern hemisphere and an increase in acute respiratory infections caused by influenza and other respiratory viruses typically observed at this time of year.  Although global activity remains within expected seasonal ranges , early increases and higher activity than typical at this time of year have been observed in some regions.  Seasonal influenza viruses, including A(H3N2) viruses, continually evolve over time.  Since August 2025, there has been a rapid increase of A(H3N2) J.2...

Key Points -- Question: What were the clinical characteristics, management approaches, and outcomes among children with influenza-associated acute necrotizing encephalopathy (ANE) in the US during the 2023-2024 and 2024-2025 influenza seasons? -- Findings:   In this multicenter case series of 41 children from 23 US hospitals , influenza-associated ANE carried a 27% mortality rate despite multimodal therapy. Most patients (76%) had no significant medical history , despite 15 of 32 tested (47%) having genetic risk alleles potentially related to risk of ANE identified during diagnostic evaluation. The H1 2009 influenza A strain predominated (34% of cases), and only 16% had received seasonal influenza vaccination . Among survivors, 63% had moderate to severe disability at 90-day follow-up. -- Meaning:  Influenza-associated ANE represents a rare but devastating neurologic complication primarily affecting previously healthy children. The high morbidity and mortality emphasize t...

Highlights •  In a landscape of a very narrow arsenal of influenza antivirals, resistance mutations are a significant threat. •  Resistance mutations were present in 0.5-5% in A and B influenza viruses during the last 15 years. •  However, S247N resistance mutation in the NA gene sharply increased during 2023-2024 season. •  While this mutation does not confer strong resistance by itself, their fixation could increase the risk of resistance in the future if other resistance mutations appears or get fixed together with it. Abstract The therapeutic arsenal against influenza is extremely limited and resistance often arises due to the emergence of mutations , especially in the neuraminidase (NA) gene. This study aimed to evaluate the evolution of NA mutations over 15 years in Spain . To do so, we used the GISAID database from which we downloaded a total of 11,125 influenza A(H1N1)pdm09, A(H3N2), B/Victoria and B/Yamagata NA virus sequences , and analyzed the resistance m...

Abstract Background :  Research on monoclonal antibodies (mAb) targeting conserved internal proteins of influenza is limited.The matrix protein 1 (M1), the most abundant and conserved internal protein, serves as an endoskeleton bridging cytoplasmic tails of envelope glycoproteins haemagglutinin (HA), neuraminidase (NA) and matrix protein 2 (M2) with viral ribonucleoprotein particles (vRNPs). Clinical studies reveal significant M1 antibody responses post-infection and vaccination, with demonstrated B and T cell recognition . Our study examines 2B-B10-G9, our lab-synthesized mAb targeting conserved linear epitope of M1 at the C-terminal domain (CTD).  Methods :  Binding of 2B-B10-G9 to the purified influenza A viruses (IAV) and influenza B viruses (IBV) were assessed using SDS-PAGE and Western blotting with Image J analysis. Purified viruses included IAV (H1N1, Pandemic ( H1N1 ) 2009 (H1N1pdm09), and H3N2 subtypes) and IBV which was first isolated in 1940 (B/Lee/40), and B/...

ABSTRACT Background and Objectives This randomised controlled trial evaluated whether higher doses of oseltamivir would improve virological and clinical outcomes in severe influenza patients requiring invasive mechanical ventilation. Methods Forty intubated adult patients with severe influenza A or B from four intensive care units in Hong Kong were enrolled and randomised to receive either a double dose (300 mg/day) or a triple dose (450 mg/day) of oseltamivir for 10 days. Baseline data were collected, and outcomes were assessed daily using SOFA and Murray scores. Viral RNA was quantified from nasopharyngeal and tracheal aspirates. The primary outcome was the viral clearance rate after 5 days of treatment; secondary outcomes included 28-day and hospital mortality rates, changes in viral load, and serial SOFA and Murray scores. Results Viral clearance rates after 5 days of treatment were low and similar between the double (3/20, 15%) and triple-dose groups (2/20, 10%). No significant di...