| 1249 | Humans |
| 623 | Influenza, Human (epidemiology) |
| 578 | Female |
| 513 | Male |
| 504 | Influenza, Human (prevention & control) |
| 469 | Adult |
| 426 | Middle Aged |
| 397 | Canada |
| 395 | Aged |
| 375 | Canada (epidemiology) |
| 356 | Adolescent |
| 334 | Child |
| 281 | Child, Preschool |
| 235 | Influenza Vaccines (administration & dosage) |
| 235 | Infant |
| 214 | Young Adult |
| 208 | Influenza, Human (virology) |
| 206 | Animals |
| 174 | Disease Outbreaks |
| 165 | Ontario (epidemiology) |
| 164 | Influenza A Virus, H1N1 Subtype |
| 154 | Aged, 80 and over |
| 153 | Seasons |
| 137 | Ontario |
| 114 | Risk Factors |
| 110 | Infant, Newborn |
| 108 | Influenza Vaccines (immunology) |
| 108 | Disease Outbreaks (prevention & control) |
| 99 | Influenza A virus (isolation & purification) |
| 94 | Influenza A Virus, H1N1 Subtype (isolation & purification) |
| 90 | Vaccination (statistics & numerical data) |
| 90 | Influenza Vaccines (adverse effects) |
| 89 | Retrospective Studies |
| 88 | Incidence |
| 86 | Surveys and Questionnaires |
| 86 | Pandemics |
| 84 | Influenza, Human (diagnosis) |
| 80 | Influenza Vaccines (therapeutic use) |
| 80 | Influenza A Virus, H1N1 Subtype (immunology) |
| 79 | Influenza, Human (immunology) |
| 73 | Influenza Vaccines |
| 70 | Population Surveillance |
| 70 | Antiviral Agents (therapeutic use) |
| 70 | Age Factors |
| 69 | Hospitalization (statistics & numerical data) |
| 68 | Time Factors |
| 67 | Pregnancy |
| 63 | Vaccination |
| 63 | United States |
| 63 | Influenza, Human (transmission) |
| 63 | Influenza, Human (drug therapy) |
| 58 | Cross-Sectional Studies |
| 56 | Influenza, Human (mortality) |
| 55 | Influenza in Birds (epidemiology) |
| 54 | Orthomyxoviridae Infections (veterinary) |
| 53 | Prospective Studies |
| 53 | Influenza A virus (immunology) |
| 52 | Phylogeny |
| 51 | Health Knowledge, Attitudes, Practice |
| 50 | Swine |
| 50 | Alberta |
| 49 | Influenza, Human (therapy) |
| 48 | Quebec |
| 48 | Pandemics (prevention & control) |
| 48 | Influenza A virus |
| 46 | Influenza B virus (isolation & purification) |
| 45 | Treatment Outcome |
| 45 | Quebec (epidemiology) |
| 45 | Influenza, Human (complications) |
| 45 | Cohort Studies |
| 44 | Influenza in Birds (virology) |
| 44 | Case-Control Studies |
| 43 | Hemagglutination Inhibition Tests |
| 43 | Antibodies, Viral (blood) |
| 42 | Sentinel Surveillance |
| 42 | Prevalence |
| 42 | Influenza A virus (genetics) |
| 41 | Population Surveillance (methods) |
| 41 | Influenza A virus (classification) |
| 40 | Orthomyxoviridae Infections (epidemiology) |
| 39 | Age Distribution |
| 38 | Hospitalization |
| 38 | Disease Outbreaks (veterinary) |
| 37 | Risk Assessment |
| 37 | Respiratory Tract Infections (epidemiology) |
| 35 | Molecular Sequence Data |
| 35 | Logistic Models |
| 35 | Attitude of Health Personnel |
| 34 | Sequence Analysis, DNA |
| 33 | Manitoba (epidemiology) |
| 33 | Influenza A Virus, H1N1 Subtype (genetics) |
| 33 | Immunization Programs |
| 33 | Alberta (epidemiology) |
| 32 | Orthomyxoviridae Infections (virology) |
| 32 | Health Personnel |
| 31 | United States (epidemiology) |
| 31 | Swine Diseases (virology) |
| 31 | Public Health |
| 31 | British Columbia |
| 31 | British Columbia (epidemiology) |
| 30 | History, 20th Century |
| 29 | Orthomyxoviridae (isolation & purification) |
| 29 | Immunization Programs (statistics & numerical data) |
| 28 | Swine Diseases (epidemiology) |
| 28 | Influenza B virus (immunology) |
| 28 | Influenza A Virus, H3N2 Subtype (isolation & purification) |
| 28 | Amantadine (therapeutic use) |
| 27 | Risk |
| 27 | Respiratory Tract Infections (virology) |
| 27 | Influenza, Human (history) |
| 27 | Comorbidity |
| 26 | Socioeconomic Factors |
| 26 | RNA, Viral (genetics) |
| 26 | Models, Theoretical |
| 26 | Influenza B virus |
| 25 | Influenza A Virus, H3N2 Subtype |
| 25 | Health Policy |
| 25 | Cost-Benefit Analysis |
| 25 | Birds |
| 24 | Influenza Vaccines (supply & distribution) |
| 24 | Influenza Vaccines (economics) |
| 23 | Sensitivity and Specificity |
| 23 | Long-Term Care |
| 23 | Influenza A virus (pathogenicity) |
| 23 | Influenza A Virus, H3N2 Subtype (immunology) |
| 23 | Emergency Service, Hospital (statistics & numerical data) |
| 22 | Vaccination (methods) |
| 21 | Severity of Illness Index |
| 21 | Practice Guidelines as Topic |
| 21 | Manitoba |
| 21 | Influenza A Virus, H3N2 Subtype (genetics) |
| 20 | Reverse Transcriptase Polymerase Chain Reaction |
| 20 | Qualitative Research |
| 20 | Pandemics (statistics & numerical data) |
| 20 | Nursing Homes |
| 20 | Models, Statistical |
| 20 | Influenza, Human (microbiology) |
| 20 | Disease Outbreaks (statistics & numerical data) |
| 20 | Disaster Planning (organization & administration) |
| 20 | Cross Infection (prevention & control) |
| 19 | Sex Factors |
| 19 | Severe Acute Respiratory Syndrome (epidemiology) |
| 19 | Odds Ratio |
| 19 | Influenza in Birds (transmission) |
| 19 | Infection Control (methods) |
| 19 | Cross Infection (epidemiology) |
| 18 | Oseltamivir (therapeutic use) |
| 18 | Immunization Programs (organization & administration) |
| 18 | Decision Making |
| 18 | Attitude to Health |
| 17 | Vaccines, Inactivated (immunology) |
| 17 | Seroepidemiologic Studies |
| 17 | Respiratory Tract Diseases (epidemiology) |
| 17 | Reproducibility of Results |
| 17 | Program Evaluation |
| 17 | Outcome Assessment, Health Care |
| 17 | Interviews as Topic |
| 17 | Influenza, Human |
| 17 | Influenza, Human (economics) |
| 17 | Influenza B virus (genetics) |
| 17 | Influenza A Virus, H1N1 Subtype (pathogenicity) |
| 17 | Immunization Schedule |
| 17 | Hemagglutinin Glycoproteins, Influenza Virus (genetics) |
| 17 | Health Surveys |
| 17 | Health Care Surveys |
| 17 | Disease Outbreaks (history) |
| 17 | Absenteeism |
| 16 | Travel |
| 16 | Rural Population |
| 16 | Pregnancy Complications, Infectious (prevention & control) |
| 16 | Pilot Projects |
| 16 | Patient Acceptance of Health Care |
| 16 | National Health Programs |
| 16 | Multivariate Analysis |
| 16 | Europe |
| 16 | Data Collection |
| 16 | Computer Simulation |
| 15 | Viral Proteins (genetics) |
| 15 | Vaccines, Inactivated (administration & dosage) |
| 15 | Vaccination (standards) |
| 15 | Vaccination (psychology) |
| 15 | Pneumococcal Infections (prevention & control) |
| 15 | Orthomyxoviridae (immunology) |
| 15 | Models, Biological |
| 15 | Influenza, Human (ethnology) |
| 15 | Influenza in Birds (prevention & control) |
| 15 | Immunization |
| 15 | Follow-Up Studies |
| 15 | Europe (epidemiology) |
| 15 | Epidemiological Monitoring |
| 15 | Epidemics |
| 15 | Drug Resistance, Viral |
| 15 | Disaster Planning |
| 14 | Poultry Diseases (epidemiology) |
| 14 | Pneumonia (epidemiology) |
| 14 | Neuraminidase (genetics) |
| 14 | Intensive Care Units |
| 14 | Health Behavior |
| 14 | Adjuvants, Immunologic (administration & dosage) |
| 13 | Urban Population |
| 13 | Syndrome |
| 13 | Respiratory Tract Diseases (etiology) |
| 13 | Pregnancy Complications, Infectious (epidemiology) |
| 13 | Patient Compliance |
| 13 | Internet |
| 13 | Influenza, Human (pathology) |
| 13 | Indians, North American (statistics & numerical data) |
| 13 | Immunization Programs (standards) |
| 13 | Immunization (statistics & numerical data) |
| 13 | Horses |
| 13 | Health Planning |
| 13 | Databases, Factual |
| 13 | Communicable Diseases (epidemiology) |
| 13 | Communicable Disease Control (methods) |
| 13 | Acute Disease |
| 12 | United Kingdom |
| 12 | Registries |
| 12 | Poultry |
| 12 | Orthomyxoviridae Infections (transmission) |
| 12 | Orthomyxoviridae (classification) |
| 12 | Nova Scotia |
| 12 | Neutralization Tests |
| 12 | Nasopharynx (virology) |
| 12 | Influenza B virus (classification) |
| 12 | Influenza A Virus, H1N1 Subtype (classification) |
| 12 | Health Status |
| 12 | Health Services Accessibility |
| 12 | Focus Groups |
| 12 | Community-Acquired Infections (epidemiology) |
| 12 | Antigens, Viral (immunology) |
| 12 | Antigens, Viral (analysis) |
| 12 | Animals, Wild (virology) |
| 11 | Workforce |
| 11 | Vaccination (adverse effects) |
| 11 | Turkeys |
| 11 | Species Specificity |
| 11 | Schools |
| 11 | Public Health Administration |
| 11 | Poultry Diseases (virology) |
| 11 | Oseltamivir |
| 11 | Orthomyxoviridae |
| 11 | Linear Models |
| 11 | Length of Stay |
| 11 | Influenza A Virus, H5N1 Subtype |
| 11 | Health Personnel (psychology) |
| 11 | Genotype |
| 11 | Cluster Analysis |
| 11 | Chronic Disease |
| 11 | Base Sequence |
| 11 | Antiviral Agents (administration & dosage) |
| 11 | Animals, Wild |
| 10 | Virus Diseases (virology) |
| 10 | Virus Diseases (epidemiology) |
| 10 | Sex Distribution |
| 10 | Severe Acute Respiratory Syndrome (prevention & control) |
| 10 | Respiratory Tract Infections (veterinary) |
| 10 | Respiratory Tract Infections (diagnosis) |
| 10 | Residence Characteristics |
| 10 | Regression Analysis |
| 10 | Public Opinion |
| 10 | Polymerase Chain Reaction |
| 10 | Patient Selection |
| 10 | Patient Acceptance of Health Care (statistics & numerical data) |
| 10 | Nova Scotia (epidemiology) |
| 10 | Mutation |
| 10 | Longitudinal Studies |
| 10 | Influenza, Human (psychology) |
| 10 | Influenza A Virus, H5N1 Subtype (genetics) |
| 10 | Influenza A Virus, H1N1 Subtype (drug effects) |
| 10 | Indians, North American |
| 10 | History, 21st Century |
| 10 | Health Personnel (statistics & numerical data) |
| 10 | Global Health |
| 10 | Family Practice |
| 10 | Eye Diseases (etiology) |
| 10 | Emergency Service, Hospital |
| 10 | Ducks (virology) |
| 10 | Contraindications |
| 10 | Confidence Intervals |
| 10 | Communication |
| 10 | Birds (virology) |
| 10 | Antiviral Agents (pharmacology) |
| 10 | Antibodies, Viral (analysis) |
| 10 | Anti-Bacterial Agents (therapeutic use) |
| 10 | Amino Acid Sequence |
| 9 | Virulence |
| 9 | Vaccines, Inactivated (adverse effects) |
| 9 | Vaccination (economics) |
| 9 | Reassortant Viruses (genetics) |
| 9 | Public Health Practice |
| 9 | Pneumonia, Viral (epidemiology) |
| 9 | Pneumonia (mortality) |
| 9 | Intensive Care Units (statistics & numerical data) |
| 9 | Influenza, Human (etiology) |
| 9 | Influenza Vaccines (standards) |
| 9 | Immunization Programs (economics) |
| 9 | Horse Diseases (epidemiology) |
| 9 | Health Services Research |
| 9 | Genome, Viral |
| 9 | Data Collection (methods) |
| 9 | Critical Illness |
| 9 | Complement Fixation Tests |
| 9 | Communicable Disease Control |
| 9 | Clinical Trials as Topic |
| 9 | Animal Migration |
| 9 | Algorithms |
| 8 | Zanamivir |
| 8 | Serologic Tests |
| 8 | Saskatchewan (epidemiology) |
| 8 | Pyrans |
| 8 | Prognosis |
| 8 | Pregnancy Complications, Infectious (virology) |
| 8 | Patient Education as Topic |
| 8 | Patient Admission |
| 8 | Patient Admission (statistics & numerical data) |
| 8 | Organizational Policy |
| 8 | Newfoundland and Labrador (epidemiology) |
| 8 | Neuraminidase (antagonists & inhibitors) |
| 8 | Mortality |
| 8 | Mice |
| 8 | Information Dissemination |
| 8 | Influenza, Human (physiopathology) |
| 8 | Influenza A Virus, H3N2 Subtype (classification) |
| 8 | Hospitalization (trends) |
| 8 | Health Services Needs and Demand |
| 8 | Guanidines |
| 8 | Genes, Viral |
| 8 | Family Characteristics |
| 8 | Evidence-Based Medicine |
| 8 | Electronic Health Records |
| 8 | Disease Outbreaks (economics) |
| 8 | Costs and Cost Analysis |
| 8 | Cooperative Behavior |
| 8 | Chickens |
| 8 | Cell Line |
| 8 | Antiviral Agents (adverse effects) |
| 8 | Antibodies, Viral (immunology) |
| 7 | World Health Organization |
| 7 | Viruses (isolation & purification) |
| 7 | Swine Diseases (transmission) |
| 7 | Survival Analysis |
| 7 | Sialic Acids (therapeutic use) |
| 7 | Serotyping |
| 7 | Sentinel Surveillance (veterinary) |
| 7 | Respiratory Syncytial Virus Infections (epidemiology) |
| 7 | Randomized Controlled Trials as Topic |
| 7 | Primary Health Care |
| 7 | Pregnancy Outcome |
| 7 | Predictive Value of Tests |
| 7 | Practice Patterns, Physicians' (statistics & numerical data) |
| 7 | Poultry (virology) |
| 7 | Pneumonia, Pneumococcal (prevention & control) |
| 7 | Pneumococcal Vaccines (administration & dosage) |
| 7 | Pneumococcal Infections (epidemiology) |
| 7 | Office Visits (statistics & numerical data) |
| 7 | Nurse's Role |
| 7 | Needs Assessment |
| 7 | Mutation, Missense |
| 7 | Military Personnel |
| 7 | Mass Vaccination (statistics & numerical data) |
| 7 | International Cooperation |
| 7 | Influenza A Virus, H5N1 Subtype (pathogenicity) |
| 7 | Influenza A Virus, H1N1 Subtype (physiology) |
| 7 | Infection Control (organization & administration) |
| 7 | Hospitals, Pediatric |
| 7 | Hospitals (statistics & numerical data) |
| 7 | Hemagglutinin Glycoproteins, Influenza Virus (immunology) |
| 7 | Health Promotion |
| 7 | Genetic Variation |
| 7 | Evolution, Molecular |
| 7 | Ducks (microbiology) |
| 7 | Drug Utilization |
| 7 | Drug Combinations |
| 7 | Disease Transmission, Infectious (prevention & control) |
| 7 | Demography |
| 7 | Critical Care |
| 7 | Cost of Illness |
| 7 | Clinical Laboratory Techniques |
| 7 | Chickens (virology) |
| 7 | Asthma (epidemiology) |
| 7 | Antiviral Agents (supply & distribution) |
| 7 | Analysis of Variance |
| 7 | Alaska (epidemiology) |
| 7 | Acetamides (therapeutic use) |
| 6 | Zoonoses |
| 6 | Yukon Territory (epidemiology) |
| 6 | World War I |
| 6 | Urban Health |
| 6 | Universities |
| 6 | Telephone |
| 6 | Squalene (administration & dosage) |
| 6 | Safety |
| 6 | Risk Assessment (methods) |
| 6 | Respiratory Tract Infections (prevention & control) |
| 6 | Respiratory Tract Infections (microbiology) |
| 6 | Respiratory Tract Infections (drug therapy) |
| 6 | Respiration, Artificial |
| 6 | Research Design |
| 6 | Reassortant Viruses (isolation & purification) |
| 6 | Real-Time Polymerase Chain Reaction |
| 6 | Quality of Life |
| 6 | Public Health Surveillance (methods) |
| 6 | Public Health (methods) |
| 6 | Preventive Health Services (statistics & numerical data) |
| 6 | Polysorbates (administration & dosage) |
| 6 | Policy Making |
| 6 | Pneumonia, Viral (veterinary) |
| 6 | Pneumonia, Pneumococcal (epidemiology) |
| 6 | Physicians |
| 6 | Oseltamivir (administration & dosage) |
| 6 | Neuraminidase (immunology) |
| 6 | Models, Economic |
| 6 | Masks |
| 6 | Influenza A virus (physiology) |
| 6 | Influenza A Virus, H5N2 Subtype (isolation & purification) |
| 6 | Influenza A Virus, H5N1 Subtype (isolation & purification) |
| 6 | Influenza A Virus, H3N2 Subtype (pathogenicity) |
| 6 | Hospitals |
| 6 | Homes for the Aged |
| 6 | History, 19th Century |
| 6 | Health Facilities |
| 6 | Guidelines as Topic |
| 6 | Geography |
| 6 | Family Practice (statistics & numerical data) |
| 6 | Eye Diseases (epidemiology) |
| 6 | Emergency Service, Hospital (organization & administration) |
| 6 | Drug-Related Side Effects and Adverse Reactions (epidemiology) |
| 6 | Dogs |
| 6 | Disease Reservoirs |
| 6 | Disease Reservoirs (veterinary) |
| 6 | Disease Outbreaks (epidemiology) |
| 6 | Communicable Diseases, Emerging (epidemiology) |
| 6 | Australia |
| 6 | Asthma (complications) |
| 6 | Antiviral Agents (economics) |
| 6 | Antigens, Viral (genetics) |
| 6 | Antigenic Variation |
| 6 | Aging |
| 6 | Advisory Committees |
| 6 | Adjuvants, Immunologic (adverse effects) |
| 5 | alpha-Tocopherol (administration & dosage) |
| 5 | Zanamivir (therapeutic use) |
| 5 | Viral Load |
| 5 | Turkeys (virology) |
| 5 | Triage |
| 5 | Triage (methods) |
| 5 | Temperature |
| 5 | Swine Diseases (microbiology) |
| 5 | Swine Diseases (immunology) |
| 5 | Swine (virology) |
| 5 | Streptococcus pneumoniae (isolation & purification) |
| 5 | Social Class |
| 5 | Skilled Nursing Facilities |
| 5 | Sequence Homology |
| 5 | Self Report |
| 5 | Self Care (methods) |
| 5 | Rhinovirus (isolation & purification) |
| 5 | Respiratory Tract Infections |
| 5 | Respiratory Tract Infections (mortality) |
| 5 | Respiratory Tract Infections (etiology) |
| 5 | Residence Characteristics (statistics & numerical data) |
| 5 | Recurrence |
| 5 | Reassortant Viruses |
| 5 | Public Health Surveillance |
| 5 | Public Health Administration (methods) |
| 5 | Primary Health Care (statistics & numerical data) |
| 5 | Premature Birth (epidemiology) |
| 5 | Practice Patterns, Physicians' |
| 5 | Population Density |
| 5 | Poisson Distribution |
| 5 | Pneumonia, Viral (virology) |
| 5 | Pneumococcal Vaccines |
| 5 | Physicians, Family |
| 5 | Paramyxoviridae Infections |
| 5 | Paramyxoviridae Infections (virology) |
| 5 | Paramyxoviridae Infections (epidemiology) |
| 5 | Orthomyxoviridae Infections (microbiology) |
| 5 | Orthomyxoviridae Infections (immunology) |
| 5 | Orthomyxoviridae Infections (diagnosis) |
| 5 | Orthomyxoviridae (genetics) |
| 5 | Organizational Case Studies |
| 5 | Nose (virology) |
| 5 | Motivation |
| 5 | Military Medicine |
| 5 | Microbial Sensitivity Tests |
| 5 | Mexico (epidemiology) |
| 5 | Mass Vaccination |
| 5 | Mass Screening |
| 5 | Mass Media |
| 5 | Mandatory Programs |
| 5 | Lung (pathology) |
| 5 | Laboratories |
| 5 | Influenza, Human (classification) |
| 5 | Influenza Vaccines (pharmacology) |
| 5 | Influenza B virus (drug effects) |
| 5 | Influenza A Virus, H5N2 Subtype (pathogenicity) |
| 5 | Influenza A Virus, H5N2 Subtype (genetics) |
| 5 | Infectious Disease Transmission, Professional-to-Patient (prevention & control) |
| 5 | Infectious Disease Transmission, Patient-to-Professional (prevention & control) |
| 5 | Infection Control |
