| 2846 | Humans |
| 1726 | Influenza, Human (epidemiology) |
| 1271 | Influenza |
| 1105 | Influenza, Human (prevention & control) |
| 901 | Female |
| 808 | Influenza A virus |
| 766 | Adult |
| 732 | Animals |
| 731 | Male |
| 730 | Human |
| 717 | Influenza A |
| 646 | Child |
| 639 | Influenza, Human (virology) |
| 628 | Vaccine |
| 626 | Public health |
| 577 | Middle Aged |
| 534 | Pandemics |
| 525 | Adolescent |
| 523 | H1N1 influenza |
| 501 | Vaccination |
| 485 | Disease Outbreaks (prevention & control) |
| 457 | Influenza A Virus, H1N1 Subtype |
| 447 | Disease Outbreaks |
| 434 | Infection |
| 427 | Young Adult |
| 421 | Aged |
| 403 | Prevention |
| 402 | Epidemiology |
| 350 | Child, Preschool |
| 339 | History, 20th Century |
| 338 | Influenza Vaccines (immunology) |
| 314 | Epidemic |
| 308 | Influenza, Human (transmission) |
| 301 | Influenza Vaccines (administration & dosage) |
| 301 | Infant |
| 301 | Antiviral |
| 295 | Influenza A (H1N1) |
| 288 | Influenza A Virus, H1N1 Subtype (immunology) |
| 284 | Influenza, Human (mortality) |
| 268 | Influenza, Human (history) |
| 261 | Antiviral Agents (therapeutic use) |
| 255 | Immunoprophylaxis |
| 254 | United States |
| 245 | Influenza, Human (drug therapy) |
| 243 | Influenza A Virus, H1N1 Subtype (isolation & purification) |
| 236 | Pandemics (prevention & control) |
| 231 | Influenza, Human (immunology) |
| 230 | United States (epidemiology) |
| 196 | Sanitary surveillance |
| 193 | Influenza A Virus, H1N1 Subtype (genetics) |
| 187 | Influenzavirus A(H1N1) |
| 187 | Aged, 80 and over |
| 184 | Pregnancy |
| 183 | Medicine |
| 183 | Avian influenza |
| 180 | Influenza, Human (diagnosis) |
| 178 | Swine |
| 171 | Influenzavirus |
| 171 | Infant, Newborn |
| 170 | Oseltamivir |
| 168 | France |
| 166 | Treatment |
| 163 | Mice |
| 159 | Seasons |
| 156 | Risk Factors |
| 154 | Global Health |
| 152 | Microbiology |
| 150 | 2009 |
| 144 | Influenza, Human (therapy) |
| 144 | Birds |
| 143 | Influenza, Human (complications) |
| 141 | Time Factors |
| 141 | Disease Outbreaks (history) |
| 138 | Influenza A Virus, H1N1 Subtype (pathogenicity) |
| 132 | Avian influenzavirus |
| 127 | Incidence |
| 124 | Pediatrics |
| 124 | Hospitalization |
| 122 | Influenza A Virus, H5N1 Subtype (immunology) |
| 122 | Europe |
| 119 | World |
| 119 | Influenza A virus (genetics) |
| 113 | Surveys and Questionnaires |
| 113 | Antibodies, Viral (blood) |
| 112 | Animal |
| 111 | Public Health |
| 111 | Orthomyxoviridae Infections (virology) |
| 110 | Influenza Vaccines |
| 108 | Influenza A Virus, H5N1 Subtype |
| 106 | Virus |
| 106 | Influenza in Birds (epidemiology) |
| 106 | Hemagglutinin Glycoproteins, Influenza Virus (genetics) |
| 105 | Influenza Vaccines (therapeutic use) |
| 105 | Disaster Planning (organization & administration) |
| 104 | Mutation |
| 103 | Transmission |
| 103 | Mouse |
| 103 | Mice, Inbred BALB C |
| 102 | Hemagglutinin |
| 101 | Disaster Planning |
| 100 | Mortality |
| 99 | Retrospective Studies |
| 98 | Review |
| 98 | Influenza A Virus, H5N1 Subtype (pathogenicity) |
| 98 | Disease Outbreaks (statistics & numerical data) |
| 97 | Models, Theoretical |
| 97 | Cross-Sectional Studies |
| 96 | World Health Organization |
| 96 | Prognosis |
| 96 | Pandemics (statistics & numerical data) |
| 95 | Seasonal variation |
| 95 | Influenza in Birds (virology) |
| 95 | Detection |
| 94 | Health Knowledge, Attitudes, Practice |
| 94 | Age Factors |
| 93 | Influenza Vaccines (supply & distribution) |
| 93 | Immunological adjuvant |
| 92 | Diagnosis |
| 91 | Models, Biological |
| 90 | Risk factor |
| 88 | Virulence |
| 88 | Pandemics (history) |
| 88 | Influenza Vaccines (adverse effects) |
| 88 | Immunogenicity |
| 87 | Resistance |
| 87 | Immune response |
| 87 | Age Distribution |
| 86 | Veterinary |
| 86 | Hemagglutinin Glycoproteins, Influenza Virus (immunology) |
| 83 | Influenza in Birds (prevention & control) |
| 83 | Hospitalization (statistics & numerical data) |
| 83 | Check |
| 82 | Risk |
| 82 | Orthomyxoviridae Infections (prevention & control) |
| 81 | Phylogeny |
| 81 | Intensive care |
| 79 | Prevalence |
| 79 | Population Surveillance |
| 79 | Orthomyxoviridae Infections (immunology) |
| 79 | Molecular Sequence Data |
| 79 | Models, Statistical |
| 79 | Computer Simulation |
| 78 | Surveillance |
| 78 | Cell Line |
| 77 | Influenza A virus (pathogenicity) |
| 77 | Influenza A virus (immunology) |
| 77 | Attitude of Health Personnel |
| 76 | Virology |
| 76 | Immunization |
| 74 | Influenza A Virus, H1N1 Subtype (physiology) |
| 74 | Hospital |
| 74 | Health Policy |
| 73 | Vaccination (statistics & numerical data) |
| 73 | Influenzavirus A(H5N1) |
| 73 | Exo-α-sialidase |
| 73 | China |
| 72 | Viral disease |
| 71 | Toxicity |
| 71 | Risk Assessment |
| 71 | Resuscitation |
| 69 | Tropical medicine |
| 69 | Hemagglutination Inhibition Tests |
| 69 | Antibodies, Viral (immunology) |
| 67 | Influenza Pandemic, 1918-1919 (history) |
| 66 | Severity of Illness Index |
| 66 | Poultry |
| 66 | Pandemic |
| 66 | Communicable Disease Control (methods) |
| 65 | Method |
| 65 | Influenza A Virus, H5N1 Subtype (genetics) |
| 65 | Comparative study |
| 65 | Antiviral Agents (pharmacology) |
| 64 | Pneumonia |
| 63 | Subtype |
| 63 | Influenza, Human (economics) |
| 63 | Influenza in Birds (transmission) |
| 63 | Antibody |
| 62 | Reverse transcription polymerase chain reaction |
| 62 | Population Surveillance (methods) |
| 61 | Oseltamivir (therapeutic use) |
| 60 | Disease Models, Animal |
| 59 | United Kingdom |
| 59 | Treatment Outcome |
| 59 | Neuraminidase (genetics) |
| 59 | Neuraminidase (antagonists & inhibitors) |
| 59 | Influenza A Virus, H1N1 Subtype (drug effects) |
| 59 | Health care staff |
| 59 | China (epidemiology) |
| 58 | Influenza, Human (pathology) |
| 58 | Efficiency |
| 58 | Dogs |
| 57 | Communication |
| 57 | Australia (epidemiology) |
| 56 | Symptomatology |
| 55 | Australia |
| 54 | Cohort Studies |
| 53 | Influenza Vaccines (genetics) |
| 53 | History, 21st Century |
| 53 | Drug Resistance, Viral |
| 53 | Antiviral Agents (administration & dosage) |
| 52 | Lung (virology) |
| 51 | Health staff |
| 50 | Survival Analysis |
| 50 | Prospective Studies |
| 50 | Humoral immunity |
| 49 | Viral Proteins (genetics) |
| 49 | Survey |
| 49 | RNA, Viral (genetics) |
| 49 | Europe (epidemiology) |
| 49 | Communicable Disease Control (organization & administration) |
| 48 | Health |
| 48 | Canada |
| 47 | Recommendation |
| 47 | Obstetrics |
| 47 | Modeling |
| 47 | Influenza A virus (classification) |
| 47 | Antiviral Agents (supply & distribution) |
| 47 | Amino Acid Sequence |
| 46 | Virus Replication |
| 46 | Travel |
| 46 | Health policy |
| 46 | Gynecology |
| 46 | Absenteeism |
| 45 | Vaccination (methods) |
| 45 | Respiratory tract |
| 45 | Hygiene |
| 45 | Gene |
| 45 | Disease |
| 45 | Antigens, Viral (immunology) |
| 44 | Sensitivity and Specificity |
| 44 | Real time |
| 44 | AIDS |
| 43 | United Kingdom (epidemiology) |
| 43 | Sentinel Surveillance |
| 43 | Reverse Transcriptase Polymerase Chain Reaction |
| 43 | Influenza, Human (psychology) |
| 43 | Inactivated strain |
| 42 | Influenza A virus (physiology) |
| 42 | Evaluation |
| 42 | Disaster Planning (methods) |
| 42 | Age |
| 41 | Genetic reassortment |
| 40 | Spain |
| 40 | Nosocomial infection |
| 40 | Models |
| 40 | Hemagglutinin Glycoproteins, Influenza Virus (metabolism) |
| 40 | Drug |
| 40 | Acute |
| 39 | Woman |
| 39 | WHO |
| 39 | Reassortant Viruses (genetics) |
| 39 | Polymerase chain reaction |
| 39 | Neutralization Tests |
| 39 | Hong Kong |
| 39 | Health Planning |
| 39 | Flulike syndrome |
| 39 | Case history |
| 39 | Care |
| 39 | Attenuated strain |
| 39 | Antigen |
| 39 | Adjuvants, Immunologic (administration & dosage) |
| 38 | Zanamivir |
| 38 | Socioeconomic Factors |
| 38 | Pathogenicity |
| 38 | Influenza Pandemic, 1918-1919 (mortality) |
| 38 | Hemagglutinin Glycoproteins, Influenza Virus (chemistry) |
| 38 | Forecasting |
| 37 | Respiratory disease |
| 37 | Influenza A virus (isolation & purification) |
| 37 | Infection Control (methods) |
| 37 | In vitro |
| 37 | Hong Kong (epidemiology) |
| 37 | Germany |
| 37 | Ferrets |
| 37 | Emergency |
| 37 | Anesthesia |
| 36 | Typing |
| 36 | Population |
| 36 | Planning |
| 36 | Orthomyxoviridae (immunology) |
| 36 | Lung (pathology) |
| 36 | Japan |
| 36 | Internet |
| 36 | Influenza A Virus, H1N1 Subtype (classification) |
| 36 | Evolution, Molecular |
| 36 | Complication |
| 35 | Pig |
| 35 | Italy |
| 35 | Genotype |
| 35 | Emerging disease |
| 34 | Risk management |
| 34 | Japan (epidemiology) |
| 34 | France (epidemiology) |
| 33 | Species Specificity |
| 33 | Serology |
| 33 | School environment |
| 33 | Replication |
| 33 | Pregnancy Complications, Infectious (prevention & control) |
| 33 | Genetics |
| 33 | Elderly |
| 33 | Data Collection |
| 33 | Cost-Benefit Analysis |
| 33 | Clinical Trials as Topic |
| 33 | Chickens |
| 32 | Vaccines, Inactivated (immunology) |
| 32 | Vaccination coverage |
| 32 | Rapid technique |
| 32 | Orthomyxoviridae Infections (veterinary) |
| 32 | Orthomyxoviridae Infections (epidemiology) |
| 32 | Mexico (epidemiology) |
| 32 | Influenza Vaccines (economics) |
| 32 | Influenza A Virus, H5N1 Subtype (isolation & purification) |
| 32 | Cohort study |
| 31 | Respiratory Tract Infections (epidemiology) |
| 31 | Patient |
| 31 | Neuraminidase inhibitor |
| 31 | Influenzavirus A |
| 31 | Health Personnel |
| 31 | Epidemics |
| 31 | England (epidemiology) |
| 31 | Communicable Disease Control |
| 31 | COVID-19 |
| 30 | Vaccines, Synthetic (immunology) |
| 30 | Schools |
| 30 | Orthomyxoviridae Infections (pathology) |
| 30 | Influenza, Human (physiopathology) |
| 30 | Influenza Pandemic, 1918-1919 |
| 30 | Influenza A Virus, H3N2 Subtype (genetics) |
| 30 | Asia |
| 29 | Zoonoses (virology) |
| 29 | World War I |
| 29 | Spain (epidemiology) |
| 29 | Safety |
| 29 | Practice Guidelines as Topic |
| 29 | Pathogenesis |
| 29 | Netherlands |
| 29 | Evolution |
| 29 | England |
| 29 | Aves |
| 28 | Zoonoses (transmission) |
| 28 | Public Health Administration |
| 28 | Preparation |
| 28 | Oseltamivir (pharmacology) |
| 28 | New Zealand (epidemiology) |
| 28 | Mexico |
| 28 | Influenza A Virus, H3N2 Subtype (immunology) |
| 28 | Immunoprotection |
| 28 | Health Planning Guidelines |
| 28 | Health Care Surveys |
| 28 | Genetic vaccine |
| 28 | Disease Transmission, Infectious (prevention & control) |
| 28 | Clinical management |
| 28 | Birds (virology) |
| 27 | Vector |
| 27 | Teaching |
| 27 | Sequence Analysis, DNA |
| 27 | Protein |
| 27 | Porcine influenzavirus |
| 27 | Models, Molecular |
| 27 | Mice, Inbred C57BL |
| 27 | Interviews as Topic |
| 27 | Intensive care unit |
| 27 | History, 19th Century |
| 27 | Germany (epidemiology) |
| 27 | Ferret |
| 27 | Ethics |
| 27 | Disease Outbreaks (economics) |
| 27 | Cross Reactions |
| 27 | Crisis |
| 27 | Communicable Diseases (epidemiology) |
| 27 | Algorithms |
| 26 | Viral Load |
| 26 | Triage (methods) |
| 26 | Strain |
| 26 | Severe Acute Respiratory Syndrome (epidemiology) |
| 26 | Sensitivity |
| 26 | Orthomyxoviridae Infections (transmission) |
| 26 | Orthomyxoviridae (pathogenicity) |
| 26 | Logistic Models |
| 26 | Homotransplantation |
| 26 | Decision Making |
| 26 | Bibliographic review |
| 25 | Swine Diseases (virology) |
| 25 | Strategy |
| 25 | Public Health Practice |
| 25 | New Zealand |
| 25 | Network |
| 25 | Madin Darby Canine Kidney Cells |
| 25 | India |
| 25 | Comorbidity |
| 25 | Clinical trial |
| 25 | Attitude |
| 25 | Animal model |
| 24 | T-Lymphocyte |
| 24 | Qualitative Research |
| 24 | Public Health (methods) |
| 24 | Orthomyxoviridae (genetics) |
| 24 | Origin |
| 24 | Organization |
| 24 | Military Personnel |
| 24 | Influenza, Human |
| 24 | Influenza in Birds (immunology) |
| 24 | Influenza A Virus, H5N1 Subtype (physiology) |
| 24 | Influenza A Virus, H3N2 Subtype (isolation & purification) |
| 24 | Immunology |
| 24 | Chemotherapy |
| 24 | Canada (epidemiology) |
| 24 | Base Sequence |
| 23 | Zoonoses (epidemiology) |
| 23 | Vaccines, Attenuated (immunology) |
| 23 | Vaccination (psychology) |
| 23 | Sex Factors |
| 23 | Respiratory Tract Infections (virology) |
| 23 | Physician |
| 23 | Pandemics (economics) |
| 23 | International Cooperation |
| 23 | Intensive Care Units |
| 23 | Influenza, Human (genetics) |
| 23 | Influenza, Human (blood) |
| 23 | Identification |
| 23 | Geography |
| 23 | Genome, Viral |
| 23 | Family Characteristics |
| 23 | Centers for Disease Control and Prevention, U.S. |
| 23 | Antiviral Agents (economics) |
| 22 | Treatment efficiency |
| 22 | Receptors, Virus (metabolism) |
| 22 | Quantitative analysis |
| 22 | Ontario (epidemiology) |
| 22 | Neuraminidase (metabolism) |
| 22 | History |
| 22 | Health Behavior |
| 22 | Genetic Variation |
| 22 | Cytokine |
| 22 | Cause of Death |
| 22 | Antiviral Agents (adverse effects) |
| 22 | Antigens, Viral (genetics) |
| 22 | Antibodies, Neutralizing (blood) |
| 21 | Respiratory distress |
| 21 | Real-Time Polymerase Chain Reaction |
| 21 | Patient Acceptance of Health Care (statistics & numerical data) |
| 21 | Molecular epidemiology |
| 21 | Laboratory |
| 21 | Influenza A Virus, H1N1 Subtype (growth & development) |
| 21 | Infection Control (organization & administration) |
| 21 | Health Services Accessibility |
| 21 | Databases, Factual |
| 21 | Cross Infection (prevention & control) |
| 21 | Cost of Illness |
| 21 | Cardiology |
| 20 | Workforce |
| 20 | Viral Proteins (metabolism) |
| 20 | Viral Matrix Proteins (immunology) |
| 20 | Sequence Alignment |
| 20 | Reproducibility of Results |
| 20 | Regression Analysis |
| 20 | Quarantine |
| 20 | Protein Binding |
| 20 | Perception |
| 20 | Orthomyxoviridae (isolation & purification) |
| 20 | Orthomyxoviridae (drug effects) |
| 20 | Odds Ratio |
| 20 | Netherlands (epidemiology) |
| 20 | Models, Economic |
| 20 | Mass Vaccination |
| 20 | Italy (epidemiology) |
| 20 | Influenza B |
| 20 | Influenza A Virus, H5N1 Subtype (drug effects) |
| 20 | India (epidemiology) |
| 20 | Immunity |
| 20 | General practitioner |
| 20 | General practice |
| 20 | Enzyme Inhibitors (therapeutic use) |
| 20 | Emergency department |
| 20 | Emergencies |
| 20 | Dragging |
| 20 | Death |
| 20 | Costs |
| 20 | Communicable Diseases, Emerging (epidemiology) |
| 20 | Communicable Disease Control (history) |
| 20 | Circulatory system |
| 20 | Cell culture |
| 20 | Behavior |
| 20 | Amino Acid Substitution |
| 19 | pandemic |
| 19 | Zoonoses |
| 19 | Sanitary program |
| 19 | Registries |
| 19 | Public Opinion |
| 19 | Protein Conformation |
| 19 | Pregnancy Complications, Infectious (epidemiology) |
| 19 | Poultry Diseases (virology) |
| 19 | Plane |
| 19 | Obesity |
| 19 | Military Personnel (history) |
| 19 | Management |
| 19 | Health Planning (organization & administration) |
| 19 | Estimation |
| 19 | Disease Reservoirs |
| 19 | Contagion |
