Influenza virus — LLMpedia

Influenza virus
Dan Dou, Rebecca Revol, Henrik Östbye, Hao Wang, and Robert Daniels · CC BY 4.0 · source
Name	Influenza virus
Virus group	Orthomyxoviridae

Contents

Influenza virus is a genus of RNA viruses that cause seasonal and pandemic respiratory disease in humans and numerous animal species. Originating from segmented negative-sense genomes, these viruses have driven public health responses, vaccine development, and antiviral research across institutions such as the World Health Organization, Centers for Disease Control and Prevention, National Institutes of Health, Wellcome Trust, and Bill & Melinda Gates Foundation. Major historical events involving influenza include the 1918 influenza pandemic, the 1957 influenza pandemic, and the 2009 flu pandemic, which influenced policies at the United Nations and in national health systems like the NHS.

Virology

Influenza viruses belong to the family Orthomyxoviridae and are enveloped, pleomorphic particles typically 80–120 nm in diameter studied by laboratories such as the Roche Diagnostics virology units and visualized with instruments from Thermo Fisher Scientific and JEOL. Structural studies by groups at Massachusetts Institute of Technology, Harvard University, University of Oxford, Max Planck Society, and Cold Spring Harbor Laboratory identified the surface glycoproteins hemagglutinin and neuraminidase, and the matrix protein M1, which interact with host factors including receptors characterized in research from Stanford University, University of Cambridge, and Karolinska Institutet. Antigenic sites mapped through collaborations involving companies such as GlaxoSmithKline, Sanofi, and Pfizer inform vaccine design used by public health agencies like the European Centre for Disease Prevention and Control.

Influenza viruses are divided into types A, B, C, and D by the International Committee on Taxonomy of Viruses. Type A infects humans, birds, swine, and other mammals and is subtyped by hemagglutinin (H) and neuraminidase (N) variants; notable subtypes include H1N1 and H3N2 seen in outbreaks investigated by teams at Centers for Disease Control and Prevention, World Health Organization, Food and Agriculture Organization, American Veterinary Medical Association, and Pan American Health Organization. Type B has lineages such as Victoria and Yamagata that are monitored by surveillance networks including the Global Influenza Surveillance and Response System. Type C causes mild human disease and has been described in studies from University of Tokyo and Osaka University, while Type D primarily affects cattle and was reported by researchers at Iowa State University and University of Glasgow.

Influenza viruses possess segmented, negative-sense single-stranded RNA genomes enabling reassortment; seminal work on reassortment was done by investigators at Rockefeller University, Columbia University, University of Pennsylvania, Yale University, and Johns Hopkins University. Antigenic drift driven by point mutations is documented in long-term cohort studies associated with institutions like University College London and Imperial College London, while antigenic shift via reassortment has led to pandemics analyzed by historians at Harvard University, Princeton University, and University of Chicago. Phylogenetic analyses use datasets curated by GISAID, with computational contributions from European Bioinformatics Institute, Broad Institute, and LossLab; evolutionary rates are compared across hosts in collaborations including Cornell University and University of California, Davis.

Transmission occurs through respiratory droplets, aerosols, and fomites in settings such as schools studied by researchers at University of Michigan, workplaces monitored by Occupational Safety and Health Administration, and healthcare facilities evaluated by Mayo Clinic and Cleveland Clinic. Seasonal patterns in temperate zones documented by the National Weather Service and Met Office contrast with tropical dynamics examined by teams at Smithsonian Tropical Research Institute and Instituto Oswaldo Cruz. Surveillance partnerships among World Health Organization, national agencies like Public Health England, and academic centers enable detection of zoonotic spillover from avian reservoirs tracked by United States Department of Agriculture and Australian Department of Agriculture.

After binding sialic acid receptors on epithelial cells in the upper and lower respiratory tract, influenza viruses initiate replication and induce host responses characterized in immunology work at Scripps Research Institute, La Jolla Institute for Immunology, and Pasteur Institute. Clinical manifestations range from uncomplicated febrile illness described in clinical guidelines from American Academy of Pediatrics and American Thoracic Society to severe viral pneumonia, acute respiratory distress syndrome, and multiorgan complications reported in case series from Johns Hopkins Hospital, Mount Sinai Hospital, and Karolinska University Hospital. High-risk groups identified by population studies at Columbia University Mailman School of Public Health, Kaiser Permanente, and Harvard T.H. Chan School of Public Health include the elderly, pregnant people, and those with chronic conditions monitored in registries maintained by Centers for Medicare & Medicaid Services.

Diagnosis uses rapid antigen detection, RT-PCR assays developed by companies such as Abbott Laboratories and Roche, and viral culture methods refined at Centers for Disease Control and Prevention and academic virology labs like University of California, San Francisco. Prevention relies on annual vaccination programs coordinated by World Health Organization and implemented by national health services such as the National Health Service (England), with vaccine platforms developed by Moderna, Novavax, Sanofi, and GlaxoSmithKline. Antiviral treatment includes neuraminidase inhibitors like oseltamivir distributed by Roche and baloxavir marboxil produced by Shionogi, complemented by supportive care protocols from American Heart Association and World Medical Association. Nonpharmaceutical interventions promoted by entities such as Centers for Disease Control and Prevention and local public health departments include masking policies evaluated during the COVID-19 pandemic.