Avian influenza, commonly known as bird flu, has become a global concern once again. In this episode, Florian Krammer explains the biology of influenza A viruses, how subtypes like H5N1 are defined by their hemagglutinin and neuraminidase proteins, and why segmented genomes allow these viruses to reassort and evolve. He outlines the difference between low and highly pathogenic avian influenza, the molecular basis of increased virulence, and the historical spread of H5N1 since the late 1990s. The episode focuses on the currently circulating clade 2.3.4.4b, its global expansion through migratory birds, large outbreaks in poultry, infections in wild mammals, and the recent spread to dairy cattle. While human infections remain rare and human-to-human transmission has not been observed, the episode explains why continued monitoring is essential, how reassortment with seasonal influenza could increase risk, and why preparedness today is far stronger than it was at the start of COVID-19.
Link to USDA data on H5N1 detection in mammals in the US: https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/mammals
WHO H5N1 updates: https://www.who.int/teams/global-influenza-programme/avian-influenza/avian-a-h5n1-virus
Paper describing US human H5N1 cases: https://pmc.ncbi.nlm.nih.gov/articles/PMC12477757/
H5N1 review paper: https://pmc.ncbi.nlm.nih.gov/articles/PMC11998540/
Article about lethal H5N5 infection in Washington State: https://www.cidrap.umn.edu/avian-influenza-bird-flu/washington-state-officials-confirm-h5n5-avian-flu-patient-has-died
Support viroLOGICAL on Steady:
You can support the podcast via our German Steady page:
https://steady.page/virologisch/
Questions, feedback or topic suggestions?
Feel free to contact us at:
[email protected]Krammer laboratory information
Krammer Laboratory at the Icahn School of Medicine at Mount Sinai
https://labs.icahn.mssm.edu/krammerlab/
Ludwig Boltzmann Institute for Science Outreach and Pandemic Preparedness
Ignaz Semmelweis Institute
https://semmelweisinstitute.ac.at/
Conflict of interest statement
The Icahn School of Medicine at Mount Sinai has filed patent applications relating to influenza virus vaccines and therapeutics, SARS-CoV-2 serological assays and NDV-based SARS-CoV-2 vaccines which name me as inventor. Mount Sinai has spun out a company, CastleVax, to commercialize NDV-based SARS-CoV-2 vaccines and I am named as co-founder and scientific advisory board member of that company.
I have previously consulted for Curevac, Merck, Gritstone, Sanofi, Seqirus, GSK and Pfizer and I am currently consulting for 3rd Rock Ventures (US) and Avimex (Mexico).
My laboratory has been collaborating in the past with Pfizer on animal models of SARS-CoV-2 and with GlaxoSmithKline and VIR on the development of influenza virus vaccines and therapeutics and we are currently collaborating with Dynavax, Inspirevax and Inimmune on development of influenza virus vaccines.
My work in the on immunity and infectious diseases in the US is supported by the National Institutes of Health, but also by FluLab and Tito’s Handmade Vodka. In the past I have also received funding from the Bill and Melinda Gates Foundation, PATH and the US Department of Defense.
My work in Austria is supported by the Ludwig Boltzmann Gesellschaft and by the Ignaz Semmelweis Institute through the Medical University of Vienna.