| 404 | Animals |
| 363 | Humans |
| 193 | Influenza A virus (immunology) |
| 157 | Influenza A virus (genetics) |
| 156 | Mice |
| 121 | Influenza Vaccines (immunology) |
| 118 | Female |
| 91 | Influenza, Human (virology) |
| 90 | Influenza A Virus, H2N2 Subtype |
| 89 | Influenza, Human (epidemiology) |
| 81 | Influenza, Human (prevention & control) |
| 76 | Adult |
| 73 | Mice, Inbred BALB C |
| 69 | Influenza A Virus, H2N2 Subtype (immunology) |
| 68 | Influenza, Human (immunology) |
| 64 | Male |
| 63 | Molecular Sequence Data |
| 62 | Influenza Vaccines (administration & dosage) |
| 62 | Cold Temperature |
| 61 | Virus Replication |
| 59 | Chick Embryo |
| 59 | Adolescent |
| 58 | Influenza A Virus, H2N2 Subtype (genetics) |
| 56 | Influenza A virus (pathogenicity) |
| 55 | Vaccines, Attenuated (immunology) |
| 55 | Recombination, Genetic |
| 54 | Child |
| 53 | Hemagglutination Inhibition Tests |
| 51 | Orthomyxoviridae Infections (immunology) |
| 50 | Viral Proteins (genetics) |
| 50 | Mutation |
| 50 | Middle Aged |
| 50 | Genes, Viral |
| 50 | Amino Acid Sequence |
| 49 | Cell Line |
| 47 | Influenza A virus (classification) |
| 47 | Antibodies, Viral (blood) |
| 46 | Influenza A Virus, H1N1 Subtype (immunology) |
| 45 | Influenza A Virus, H3N2 Subtype |
| 44 | Neuraminidase (genetics) |
| 43 | Neuraminidase (immunology) |
| 43 | Influenza A virus (isolation & purification) |
| 41 | Child, Preschool |
| 40 | Orthomyxoviridae Infections (prevention & control) |
| 40 | Base Sequence |
| 40 | Antibodies, Viral (immunology) |
| 39 | Reassortant Viruses (genetics) |
| 39 | Dogs |
| 38 | Influenza Vaccines (genetics) |
| 38 | Influenza A virus (physiology) |
| 37 | Influenza in Birds (virology) |
| 36 | Antibodies, Viral (analysis) |
| 35 | Birds |
| 34 | Orthomyxoviridae (immunology) |
| 34 | Hemagglutinin Glycoproteins, Influenza Virus (genetics) |
| 34 | Cross Reactions |
| 33 | Vaccination |
| 33 | Influenza A virus (enzymology) |
| 33 | Disease Outbreaks |
| 33 | Antigens, Viral (immunology) |
| 32 | Hemagglutinins, Viral (immunology) |
| 32 | Aged |
| 31 | Orthomyxoviridae Infections (virology) |
| 31 | Influenza, Human (transmission) |
| 31 | Influenza A virus (drug effects) |
| 31 | Antiviral Agents (pharmacology) |
| 30 | Reassortant Viruses (immunology) |
| 30 | Influenza A Virus, H1N1 Subtype (genetics) |
| 30 | Antigens, Viral (analysis) |
| 29 | Vaccines, Attenuated (genetics) |
| 29 | Temperature |
| 29 | RNA, Viral (genetics) |
| 29 | Influenza Vaccines (adverse effects) |
| 29 | Infant |
| 29 | Ferrets |
| 28 | Influenza A Virus, H1N1 Subtype |
| 27 | Phylogeny |
| 27 | Influenza A Virus, H3N2 Subtype (genetics) |
| 27 | Hemagglutinin Glycoproteins, Influenza Virus (immunology) |
| 26 | Phenotype |
| 26 | Neutralization Tests |
| 26 | History, 20th Century |
| 26 | Antibodies, Viral (biosynthesis) |
| 25 | Pandemics |
| 25 | Influenza, Human (history) |
| 25 | Influenza A virus (growth & development) |
| 24 | Vaccines, Attenuated (administration & dosage) |
| 24 | Influenza A Virus, H5N1 Subtype (immunology) |
| 24 | Influenza A Virus, H3N2 Subtype (immunology) |
| 23 | Time Factors |
| 23 | Models, Molecular |
| 23 | Chickens |
| 23 | Cells, Cultured |
| 22 | Virulence |
| 22 | T-Lymphocytes, Cytotoxic (immunology) |
| 22 | Influenza, Human (mortality) |
| 22 | Influenza A Virus, H2N2 Subtype (pathogenicity) |
| 22 | Antiviral Agents (therapeutic use) |
| 22 | Adaptation, Physiological |
| 21 | Hemagglutinins, Viral (analysis) |
| 21 | Hemagglutinin Glycoproteins, Influenza Virus (metabolism) |
| 21 | Hemagglutinin Glycoproteins, Influenza Virus (chemistry) |
| 20 | RNA, Viral (analysis) |
| 20 | Influenza A Virus, H5N1 Subtype (genetics) |
| 20 | Hemagglutinins, Viral (genetics) |
| 20 | Disease Models, Animal |
| 19 | Young Adult |
| 19 | Virus Replication (drug effects) |
| 19 | Species Specificity |
| 19 | Neuraminidase (metabolism) |
| 19 | Influenza, Human (microbiology) |
| 19 | Influenza B virus (immunology) |
| 19 | Influenza A Virus, H2N2 Subtype (isolation & purification) |
| 19 | Antibodies, Monoclonal (immunology) |
| 18 | Influenza Vaccines |
| 18 | Immunization |
| 18 | Administration, Intranasal |
| 17 | Viral Proteins (analysis) |
| 17 | Viral Matrix Proteins (genetics) |
| 17 | Seasons |
| 17 | Orthomyxoviridae Infections (pathology) |
| 17 | Neuraminidase (antagonists & inhibitors) |
| 17 | Lung (virology) |
| 17 | Influenza A virus (analysis) |
| 17 | Epitopes (immunology) |
| 17 | Amino Acid Substitution |
| 16 | Vaccines, Attenuated |
| 16 | Protein Binding |
| 16 | Epitopes |
| 16 | Electrophoresis, Polyacrylamide Gel |
| 16 | Antigens, Viral (genetics) |
| 15 | Viral Proteins (metabolism) |
| 15 | Viral Plaque Assay |
| 15 | Vaccines, Attenuated (adverse effects) |
| 15 | Swine |
| 15 | Influenza in Birds (epidemiology) |
| 15 | Influenza A Virus, H2N2 Subtype (physiology) |
| 15 | Genome, Viral |
| 14 | Viral Proteins (immunology) |
| 14 | Structure-Activity Relationship |
| 14 | Russia |
| 14 | Lung (microbiology) |
| 14 | Influenza, Human (drug therapy) |
| 14 | Influenza, Human (diagnosis) |
| 14 | Influenza A virus (metabolism) |
| 14 | Genotype |
| 14 | Genetic Variation |
| 14 | Evolution, Molecular |
| 14 | Antibodies, Neutralizing (immunology) |
| 13 | Orthomyxoviridae Infections (drug therapy) |
| 13 | Lymphocyte Activation |
| 13 | Influenza in Birds (transmission) |
| 13 | Disease Outbreaks (prevention & control) |
| 13 | Disease Outbreaks (history) |
| 13 | Cricetinae |
| 13 | Binding Sites |
| 12 | Zoonoses (virology) |
| 12 | Sequence Analysis, DNA |
| 12 | Rabbits |
| 12 | Protein Conformation |
| 12 | Orthomyxoviridae (genetics) |
| 12 | Neuraminidase (chemistry) |
| 12 | Microbial Sensitivity Tests |
| 12 | Influenza A Virus, H2N2 Subtype (chemistry) |
| 12 | Infant, Newborn |
| 12 | Hemagglutinin Glycoproteins, Influenza Virus |
| 12 | CD8-Positive T-Lymphocytes (immunology) |
| 12 | Antibody Specificity |
| 11 | Vaccines, Inactivated (immunology) |
| 11 | T-Lymphocytes (immunology) |
| 11 | Sequence Alignment |
| 11 | Sensitivity and Specificity |
| 11 | Orthomyxoviridae Infections (mortality) |
| 11 | Mice, Inbred C57BL |
| 11 | Influenza, Human (genetics) |
| 11 | Influenza in Birds (prevention & control) |
| 11 | Influenza A virus |
| 11 | Influenza A Virus, H5N1 Subtype (pathogenicity) |
| 11 | Influenza A Virus, H2N2 Subtype (metabolism) |
| 11 | Hydrogen-Ion Concentration |
| 11 | Hemagglutinins, Viral |
| 11 | CD4-Positive T-Lymphocytes (immunology) |
| 11 | Antiviral Agents (chemistry) |
| 11 | Antigens, Viral |
| 11 | Antibodies, Monoclonal |
| 10 | Zoonoses (epidemiology) |
| 10 | Viral Proteins (chemistry) |
| 10 | Vaccines, Synthetic (immunology) |
| 10 | RNA Replicase (genetics) |
| 10 | Peptides (analysis) |
| 10 | Orthomyxoviridae Infections (veterinary) |
| 10 | Nucleoproteins (genetics) |
| 10 | Nucleic Acid Hybridization |
| 10 | Mutation, Missense |
| 10 | Models, Biological |
| 10 | Mice, Inbred Strains |
| 10 | Mice, Inbred CBA |
| 10 | Lung (pathology) |
| 10 | Influenza B virus (drug effects) |
| 10 | Influenza A Virus, H5N1 Subtype |
| 10 | Influenza A Virus, H1N1 Subtype (physiology) |
| 10 | Influenza A Virus, H1N1 Subtype (pathogenicity) |
| 10 | Immunoenzyme Techniques |
| 10 | Dose-Response Relationship, Drug |
| 10 | B-Lymphocytes (immunology) |
| 10 | Adamantane (analogs & derivatives) |
| 9 | United States (epidemiology) |
| 9 | Swine (virology) |
| 9 | Reverse Transcriptase Polymerase Chain Reaction |
| 9 | Receptors, Virus (metabolism) |
| 9 | Orthomyxoviridae Infections (microbiology) |
| 9 | Neuraminidase (analysis) |
| 9 | Lung (immunology) |
| 9 | Influenza in Birds (immunology) |
| 9 | Influenza Vaccines (therapeutic use) |
| 9 | Influenza B virus (genetics) |
| 9 | Influenza A virus (chemistry) |
| 9 | Influenza A Virus, H2N2 Subtype (drug effects) |
| 9 | Global Health |
| 9 | Enzyme-Linked Immunosorbent Assay |
| 9 | Chlorocebus aethiops |
| 9 | Antibody Formation |
| 9 | Aged, 80 and over |
| 9 | Adaptation, Biological |
| 8 | Viral Matrix Proteins (immunology) |
| 8 | Transfection |
| 8 | Seroepidemiologic Studies |
| 8 | Sequence Homology, Amino Acid |
| 8 | Pregnancy |
| 8 | Peptides (immunology) |
| 8 | Orthomyxoviridae (enzymology) |
| 8 | Kinetics |
| 8 | Influenza, Human (blood) |
| 8 | Influenza Vaccines (isolation & purification) |
| 8 | Influenza A Virus, H5N2 Subtype (immunology) |
| 8 | Influenza A Virus, H5N1 Subtype (isolation & purification) |
| 8 | Influenza A Virus, H3N2 Subtype (metabolism) |
| 8 | Influenza A Virus, H3N2 Subtype (chemistry) |
| 8 | Immunity, Cellular |
| 8 | Epitopes (analysis) |
| 8 | DNA, Viral (genetics) |
| 8 | Cross Reactions (immunology) |
| 8 | Cross Protection |
| 8 | China |
| 8 | Chickens (immunology) |
| 8 | Birds (virology) |
| 8 | Biological Evolution |
| 8 | Age Factors |
| 7 | Zoonoses (transmission) |
| 7 | Virus Shedding |
| 7 | Viral Nonstructural Proteins (genetics) |
| 7 | Risk Factors |
| 7 | Reassortant Viruses (physiology) |
| 7 | Prevalence |
| 7 | Orthomyxoviridae (drug effects) |
| 7 | Mutagenesis, Site-Directed |
| 7 | Mice, Transgenic |
| 7 | Lymphocytes (immunology) |
| 7 | Immunologic Memory |
| 7 | Immunization, Secondary |
| 7 | Hemagglutination Tests |
| 7 | Epitopes (genetics) |
| 7 | Enzyme Inhibitors (pharmacology) |
| 7 | Drug Evaluation, Preclinical |
| 7 | Double-Blind Method |
| 7 | Cytotoxicity, Immunologic |
| 7 | Culture Techniques |
| 7 | Crystallography, X-Ray |
| 7 | Computer Simulation |
| 7 | Computational Biology |
| 7 | Chickens (virology) |
| 7 | Antiviral Agents (chemical synthesis) |
| 7 | Antibodies, Neutralizing (blood) |
| 7 | Antibodies, Monoclonal (isolation & purification) |
| 7 | Adsorption |
| 6 | Virus Replication (genetics) |
| 6 | Viral Proteins (classification) |
| 6 | Viral Proteins (biosynthesis) |
| 6 | Viral Matrix Proteins (metabolism) |
| 6 | Vaccination (methods) |
| 6 | Survival Analysis |
| 6 | Reassortant Viruses (pathogenicity) |
| 6 | Rats |
| 6 | Pandemics (prevention & control) |
| 6 | Oseltamivir (pharmacology) |
| 6 | Orthomyxoviridae (physiology) |
| 6 | Orthomyxoviridae (pathogenicity) |
| 6 | Molecular Structure |
| 6 | Japan |
| 6 | Interferon-gamma (biosynthesis) |
| 6 | Influenza Vaccines (pharmacology) |
| 6 | Influenza A Virus, H9N2 Subtype (immunology) |
| 6 | Influenza A Virus, H7N9 Subtype (immunology) |
| 6 | Influenza A Virus, H5N2 Subtype (genetics) |
| 6 | Influenza A Virus, H5N1 Subtype (physiology) |
| 6 | Influenza A Virus, H3N2 Subtype (pathogenicity) |
| 6 | Influenza A Virus, H2N2 Subtype (growth & development) |
| 6 | Influenza A Virus, H2N2 Subtype (enzymology) |
| 6 | Influenza A Virus, H1N1 Subtype (drug effects) |
| 6 | Histocompatibility Antigens Class I (immunology) |
| 6 | Genes, Viral (genetics) |
| 6 | Epitopes, T-Lymphocyte (immunology) |
| 6 | Ducks (virology) |
| 6 | Ducks (microbiology) |
| 6 | Drug Resistance, Viral |
| 6 | Dendritic Cells (immunology) |
| 6 | DNA, Viral |
| 6 | Birds (microbiology) |
| 6 | Antibodies, Viral (isolation & purification) |
| 6 | Adaptation, Physiological (genetics) |
| 5 | World Health Organization |
| 5 | Virus Cultivation |
| 5 | Viral Load |
| 5 | Vaccines, Synthetic (genetics) |
| 5 | Vaccines, Attenuated (isolation & purification) |
| 5 | Urban Population |
| 5 | Survival Rate |
| 5 | Serial Passage |
| 5 | Rimantadine (pharmacology) |
| 5 | Reassortant Viruses (isolation & purification) |
| 5 | RNA, Messenger (genetics) |
| 5 | Population Surveillance |
| 5 | Polymerase Chain Reaction (methods) |
| 5 | Plasmids |
| 5 | Orthomyxoviridae Infections (transmission) |
| 5 | Orthomyxoviridae (growth & development) |
| 5 | Orthomyxoviridae (classification) |
| 5 | Neuraminidase (isolation & purification) |
| 5 | Mice, Inbred C3H |
| 5 | Lymph Nodes (immunology) |
| 5 | Kidney |
| 5 | Influenza, Human (metabolism) |
| 5 | Influenza B virus (physiology) |
| 5 | Influenza A Virus, H9N2 Subtype |
| 5 | Influenza A Virus, H3N2 Subtype (isolation & purification) |
| 5 | Influenza A Virus, H1N1 Subtype (enzymology) |
| 5 | Influenza A Virus, H1N1 Subtype (chemistry) |
| 5 | Immunization Schedule |
| 5 | Hong Kong |
| 5 | Hong Kong (epidemiology) |
| 5 | Hemagglutinins, Viral (chemistry) |
| 5 | Hemagglutinins (genetics) |
| 5 | Hemagglutination, Viral |
| 5 | Guinea Pigs |
| 5 | Ferrets (immunology) |
| 5 | Evaluation Studies as Topic |
| 5 | Drug Resistance, Microbial |
| 5 | Disease Reservoirs |
| 5 | Conserved Sequence |
| 5 | Clinical Trials as Topic |
| 5 | Cell Movement (immunology) |
| 5 | Antigenic Variation |
| 5 | Antibodies, Viral |
| 5 | Amantadine (therapeutic use) |
| 5 | Amantadine (pharmacology) |
| 5 | Age Distribution |
| 4 | Zoonoses |
| 4 | Viral Vaccines (immunology) |
| 4 | Viral Matrix Proteins (chemistry) |
| 4 | Viral Core Proteins (genetics) |
| 4 | Vaccines, Synthetic (administration & dosage) |
| 4 | Vaccines, Inactivated (administration & dosage) |
| 4 | USSR |
| 4 | Treatment Outcome |
| 4 | Swine Diseases (virology) |
| 4 | Swine (microbiology) |
| 4 | Stochastic Processes |
| 4 | Reverse Genetics |
| 4 | Recombinant Proteins |
| 4 | Receptors, Virus (chemistry) |
| 4 | Reassortant Viruses |
| 4 | Reassortant Viruses (growth & development) |
| 4 | RNA Replicase (metabolism) |
| 4 | Poultry |
| 4 | Poultry Diseases (virology) |
| 4 | Polysaccharides (metabolism) |
| 4 | Polymerase Chain Reaction |
| 4 | Pneumonia, Viral (pathology) |
| 4 | Pandemics (history) |
| 4 | Orthomyxoviridae Infections (epidemiology) |
| 4 | Orthomyxoviridae Infections (blood) |
| 4 | Orthomyxoviridae (metabolism) |
| 4 | Orthomyxoviridae (analysis) |
| 4 | Nucleoproteins (immunology) |
| 4 | North America |
| 4 | Mutation (genetics) |
| 4 | Molecular Dynamics Simulation |
| 4 | Mesocricetus |
| 4 | Madin Darby Canine Kidney Cells |
| 4 | Macaca mulatta |
| 4 | Influenza, Human (pathology) |
| 4 | Influenza, Human (complications) |
| 4 | Influenza A virus (radiation effects) |
| 4 | Influenza A Virus, H2N2 Subtype (classification) |
| 4 | In Vitro Techniques |
| 4 | Immunoglobulin G (blood) |
| 4 | Immunoglobulin G (analysis) |
| 4 | Immunoglobulin A (blood) |
| 4 | Immunoglobulin A (analysis) |
| 4 | Immunodiffusion |
| 4 | Immunity |
| 4 | Immune Sera (immunology) |
| 4 | Hot Temperature |
| 4 | History, 21st Century |
| 4 | History, 19th Century |
| 4 | History, 18th Century |
| 4 | Healthy Volunteers |
| 4 | HeLa Cells |
| 4 | Genetic Complementation Test |
| 4 | Gene Expression |
| 4 | Europe |
| 4 | Epitopes (chemistry) |
| 4 | Drug Administration Schedule |
| 4 | Dose-Response Relationship, Immunologic |
| 4 | Disaster Planning |
| 4 | DNA, Viral (analysis) |
| 4 | Cytopathogenic Effect, Viral |
| 4 | Cytokines (biosynthesis) |
| 4 | Cluster Analysis |
| 4 | Cloning, Molecular |
| 4 | Cloaca (virology) |
| 4 | China (epidemiology) |
| 4 | Cattle |
| 4 | Bird Diseases (virology) |
| 4 | Bird Diseases (transmission) |
| 4 | Asia |
| 4 | Antigens, Viral (chemistry) |
| 4 | Antigen-Antibody Complex |
| 4 | Amino Acids (analysis) |
| 4 | Algorithms |
| 4 | Adoptive Transfer |
| 4 | Administration, Oral |
| 4 | Adamantane (pharmacology) |
| 3 | Virus Replication (immunology) |
| 3 | Virulence (genetics) |
| 3 | Virology (methods) |
| 3 | Virion (genetics) |
| 3 | Viral Matrix Proteins |
| 3 | Vero Cells |
| 3 | Vaccinia virus (genetics) |
| 3 | Vaccines, Synthetic (adverse effects) |
| 3 | Vaccines, DNA (immunology) |
| 3 | Vaccines, Attenuated (therapeutic use) |
| 3 | United States |
| 3 | Tumor Cells, Cultured |
| 3 | Transcription, Genetic |
| 3 | Trachea (virology) |
| 3 | Trachea (microbiology) |
| 3 | Thermodynamics |
| 3 | Technology, Pharmaceutical (methods) |
| 3 | Swine Diseases (transmission) |
| 3 | Swine Diseases (immunology) |
| 3 | Spleen (immunology) |
| 3 | Sialic Acids (metabolism) |
| 3 | Sialic Acids (chemistry) |
| 3 | Severity of Illness Index |
| 3 | Serotyping |
| 3 | Sequence Homology, Nucleic Acid |
| 3 | Sequence Analysis, Protein |
| 3 | Selection, Genetic |
| 3 | Saimiri |
| 3 | Risk Assessment |
| 3 | Rimantadine (therapeutic use) |
| 3 | Ribavirin (pharmacology) |
| 3 | Respiratory System (virology) |
| 3 | Respiratory System (immunology) |
| 3 | Reproducibility of Results |
| 3 | Recurrence |
| 3 | Recombinant Proteins (metabolism) |
| 3 | Recombinant Proteins (immunology) |
| 3 | Recombinant Proteins (genetics) |
| 3 | Recombinant Fusion Proteins (immunology) |
| 3 | Receptors, Cell Surface (metabolism) |
| 3 | Reassortant Viruses (classification) |
| 3 | Real-Time Polymerase Chain Reaction (methods) |
| 3 | Radioimmunoassay |
| 3 | Radioimmunoassay (methods) |
| 3 | RNA, Viral (chemistry) |
| 3 | Protein Structure, Secondary |
| 3 | Pregnancy Complications, Infectious (prevention & control) |
| 3 | Poultry (virology) |
| 3 | Polysaccharides (chemistry) |
| 3 | Pneumonia (prevention & control) |
| 3 | Phagocytosis |
| 3 | Orthomyxoviridae Infections (genetics) |
| 3 | Orthomyxoviridae Infections (complications) |
| 3 | Nucleoproteins (classification) |
| 3 | Nucleoproteins (analysis) |
| 3 | Nose (immunology) |
| 3 | Neuraminidase |
| 3 | Neuraminidase (pharmacology) |
| 3 | Neuraminidase (biosynthesis) |
| 3 | Nasopharynx (microbiology) |
| 3 | Nasal Mucosa (immunology) |
| 3 | N-Acetylneuraminic Acid (metabolism) |
| 3 | Mutant Proteins (genetics) |
| 3 | Moscow |
| 3 | Models, Theoretical |
| 3 | Models, Genetic |
| 3 | Microarray Analysis |
