| 1248 | Humans |
| 1005 | Influenza, Human |
| 772 | Canada |
| 577 | Female |
| 513 | Male |
| 484 | Influenza Vaccines |
| 468 | Adult |
| 425 | Middle Aged |
| 396 | Aged |
| 355 | Adolescent |
| 350 | Influenza A Virus, H1N1 Subtype |
| 346 | Disease Outbreaks |
| 334 | Child |
| 302 | Ontario |
| 281 | Child, Preschool |
| 235 | Infant |
| 217 | Influenza A virus |
| 214 | Young Adult |
| 207 | Vaccination |
| 206 | Animals |
| 154 | Aged, 80 and over |
| 152 | Seasons |
| 151 | Pandemics |
| 114 | Risk Factors |
| 113 | Hospitalization |
| 111 | Population Surveillance |
| 110 | Infant, Newborn |
| 99 | Immunization Programs |
| 94 | Influenza B virus |
| 93 | United States |
| 93 | Quebec |
| 89 | Surveys and Questionnaires |
| 89 | Antiviral Agents |
| 88 | Retrospective Studies |
| 88 | Incidence |
| 84 | Influenza in Birds |
| 83 | Alberta |
| 70 | Age Factors |
| 69 | Orthomyxoviridae Infections |
| 69 | Influenza A Virus, H3N2 Subtype |
| 68 | Time Factors |
| 66 | Pregnancy |
| 64 | Respiratory Tract Infections |
| 64 | Antibodies, Viral |
| 62 | British Columbia |
| 60 | Health Personnel |
| 58 | Cross-Sectional Studies |
| 56 | Swine |
| 56 | Orthomyxoviridae |
| 55 | Manitoba |
| 53 | Prospective Studies |
| 52 | Phylogeny |
| 51 | Health Knowledge, Attitudes, Practice |
| 50 | Public Health |
| 50 | Hemagglutination Inhibition Tests |
| 49 | Sentinel Surveillance |
| 46 | Swine Diseases |
| 45 | Treatment Outcome |
| 45 | Cohort Studies |
| 44 | Case-Control Studies |
| 43 | Risk Assessment |
| 42 | Prevalence |
| 42 | Emergency Service, Hospital |
| 41 | Disaster Planning |
| 40 | Immunization |
| 39 | Birds |
| 39 | Age Distribution |
| 35 | Sequence Analysis, DNA |
| 35 | Oseltamivir |
| 35 | Molecular Sequence Data |
| 35 | Logistic Models |
| 35 | Attitude of Health Personnel |
| 35 | Antigens, Viral |
| 34 | Cross Infection |
| 33 | Infection Control |
| 32 | Europe |
| 31 | Pregnancy Complications, Infectious |
| 31 | Patient Acceptance of Health Care |
| 31 | Communicable Disease Control |
| 31 | Amantadine |
| 30 | RNA, Viral |
| 30 | History, 20th Century |
| 29 | Respiratory Tract Diseases |
| 29 | Long-Term Care |
| 29 | Health Policy |
| 28 | Influenza A Virus, H5N1 Subtype |
| 28 | Comorbidity |
| 27 | Vaccines, Inactivated |
| 27 | Risk |
| 27 | Reverse Transcriptase Polymerase Chain Reaction |
| 27 | Nursing Homes |
| 27 | Indians, North American |
| 27 | Cost-Benefit Analysis |
| 26 | Socioeconomic Factors |
| 26 | Neuraminidase |
| 26 | Models, Theoretical |
| 25 | Pneumonia |
| 25 | National Health Programs |
| 25 | Intensive Care Units |
| 25 | Data Collection |
| 25 | Animals, Wild |
| 24 | Severe Acute Respiratory Syndrome |
| 23 | Sensitivity and Specificity |
| 22 | Public Health Administration |
| 22 | Practice Guidelines as Topic |
| 22 | Nova Scotia |
| 22 | Hemagglutinin Glycoproteins, Influenza Virus |
| 22 | Ducks |
| 21 | Severity of Illness Index |
| 21 | Health Planning |
| 21 | Family Practice |
| 20 | Qualitative Research |
| 20 | Poultry |
| 20 | Poultry Diseases |
| 20 | Models, Statistical |
| 20 | Mass Vaccination |
| 20 | Health Services Accessibility |
| 20 | Epidemics |
| 20 | Adjuvants, Immunologic |
| 19 | Turkeys |
| 19 | Sex Factors |
| 19 | Outcome Assessment, Health Care |
| 19 | Odds Ratio |
| 19 | Chickens |
| 18 | Viral Proteins |
| 18 | Rural Population |
| 18 | Pneumonia, Viral |
| 18 | Interviews as Topic |
| 18 | Health Surveys |
| 18 | Epidemiological Monitoring |
| 18 | Drug Resistance, Viral |
| 18 | Decision Making |
| 18 | Attitude to Health |
| 17 | Travel |
| 17 | Seroepidemiologic Studies |
| 17 | Reproducibility of Results |
| 17 | Program Evaluation |
| 17 | Pneumococcal Vaccines |
| 17 | Pneumococcal Infections |
| 17 | Patient Admission |
| 17 | Immunization Schedule |
| 17 | Health Care Surveys |
| 17 | Computer Simulation |
| 17 | Absenteeism |
| 16 | Virus Diseases |
| 16 | Primary Health Care |
| 16 | Pilot Projects |
| 16 | Nasopharynx |
| 16 | Multivariate Analysis |
| 16 | Internet |
| 16 | Community-Acquired Infections |
| 16 | Communicable Diseases |
| 15 | Urban Population |
| 15 | Residence Characteristics |
| 15 | Reassortant Viruses |
| 15 | Polymerase Chain Reaction |
| 15 | Models, Biological |
| 15 | Length of Stay |
| 15 | Follow-Up Studies |
| 15 | Databases, Factual |
| 15 | Chronic Disease |
| 14 | Zanamivir |
| 14 | Registries |
| 14 | Preventive Health Services |
| 14 | Patient Compliance |
| 14 | Horses |
| 14 | Health Promotion |
| 14 | Health Behavior |
| 14 | Critical Illness |
| 14 | Acute Disease |
| 13 | Zoonoses |
| 13 | United Kingdom |
| 13 | Syndrome |
| 13 | Hospitals |
| 13 | Horse Diseases |
| 13 | Focus Groups |
| 13 | Eye Diseases |
| 13 | Disease Reservoirs |
| 13 | Anti-Bacterial Agents |
| 12 | Triage |
| 12 | Schools |
| 12 | Respiration, Artificial |
| 12 | Practice Patterns, Physicians' |
| 12 | Physicians, Family |
| 12 | Paramyxoviridae Infections |
| 12 | Newfoundland and Labrador |
| 12 | Neutralization Tests |
| 12 | Health Status |
| 12 | Genome, Viral |
| 12 | Critical Care |
| 12 | Asthma |
| 11 | Workforce |
| 11 | Species Specificity |
| 11 | Public Health Surveillance |
| 11 | Public Health Practice |
| 11 | Physicians |
| 11 | Patient Selection |
| 11 | Mutation |
| 11 | Linear Models |
| 11 | Hospitals, Pediatric |
| 11 | Health Services Research |
| 11 | Health Services Needs and Demand |
| 11 | Global Health |
| 11 | Genotype |
| 11 | Genes, Viral |
| 11 | Cluster Analysis |
| 11 | Base Sequence |
| 11 | Acetamides |
| 10 | Vaccines, Attenuated |
| 10 | Streptococcus pneumoniae |
| 10 | Sex Distribution |
| 10 | Regression Analysis |
| 10 | Public Opinion |
| 10 | Patient Education as Topic |
| 10 | Nurse's Role |
| 10 | Mortality |
| 10 | Mass Screening |
| 10 | Masks |
| 10 | Mandatory Programs |
| 10 | Longitudinal Studies |
| 10 | Influenza A Virus, H5N2 Subtype |
| 10 | History, 21st Century |
| 10 | Drug Utilization |
| 10 | Contraindications |
| 10 | Confidence Intervals |
| 10 | Communication |
| 10 | Communicable Diseases, Emerging |
| 10 | Clinical Trials as Topic |
| 10 | China |
| 10 | Amino Acid Sequence |
| 9 | Viruses |
| 9 | Virulence |
| 9 | Sialic Acids |
| 9 | Self Care |
| 9 | Saskatchewan |
| 9 | Pulmonary Disease, Chronic Obstructive |
| 9 | Pregnancy Outcome |
| 9 | Pneumonia, Pneumococcal |
| 9 | Pharmacists |
| 9 | Lung |
| 9 | Laboratories |
| 9 | Information Dissemination |
| 9 | Homes for the Aged |
| 9 | Hemagglutinins, Viral |
| 9 | Guideline Adherence |
| 9 | Genetic Variation |
| 9 | Evidence-Based Medicine |
| 9 | Electronic Health Records |
| 9 | Disease Notification |
| 9 | Costs and Cost Analysis |
| 9 | Complement Fixation Tests |
| 9 | Clinical Laboratory Techniques |
| 9 | Bacterial Vaccines |
| 9 | Australia |
| 9 | Antigenic Variation |
| 9 | Animal Migration |
| 9 | Algorithms |
| 8 | Yukon Territory |
| 8 | Universities |
| 8 | Serotyping |
| 8 | Serologic Tests |
| 8 | Respiratory Syncytial Virus Infections |
| 8 | Real-Time Polymerase Chain Reaction |
| 8 | Randomized Controlled Trials as Topic |
| 8 | Quarantine |
| 8 | Pyrans |
| 8 | Prognosis |
| 8 | Polysorbates |
| 8 | Parents |
| 8 | Organizational Policy |
| 8 | Office Visits |
| 8 | Occupational Health |
| 8 | Military Personnel |
| 8 | Mice |
| 8 | Mexico |
| 8 | International Cooperation |
| 8 | Guanidines |
| 8 | Family Characteristics |
| 8 | Enzyme-Linked Immunosorbent Assay |
| 8 | Delivery of Health Care |
| 8 | Cooperative Behavior |
| 8 | Commerce |
| 8 | Cell Line |
| 8 | Asia |
| 8 | Alaska |
| 7 | World Health Organization |
| 7 | Tetanus Toxoid |
| 7 | Survival Rate |
| 7 | Survival Analysis |
| 7 | Students |
| 7 | Squalene |
| 7 | Spain |
| 7 | Skilled Nursing Facilities |
| 7 | Premature Birth |
| 7 | Predictive Value of Tests |
| 7 | Personnel, Hospital |
| 7 | Nurses |
| 7 | Neoplasms |
| 7 | Needs Assessment |
| 7 | Mutation, Missense |
| 7 | Military Medicine |
| 7 | Infectious Disease Transmission, Patient-to-Professional |
| 7 | Health Services |
| 7 | Health Facilities |
| 7 | Health Education |
| 7 | Forecasting |
| 7 | Evolution, Molecular |
| 7 | Ethnic Groups |
| 7 | Drug-Related Side Effects and Adverse Reactions |
| 7 | Drug Prescriptions |
| 7 | Drug Combinations |
| 7 | Disease Transmission, Infectious |
| 7 | Diabetes Mellitus |
| 7 | Demography |
| 7 | DNA, Viral |
| 7 | Cross Reactions |
| 7 | Cost of Illness |
| 7 | Antibodies |
| 7 | Anseriformes |
| 7 | Analysis of Variance |
| 6 | alpha-Tocopherol |
| 6 | World War I |
| 6 | Virology |
| 6 | Viral Load |
| 6 | Urban Health |
| 6 | Telephone |
| 6 | Smoking |
| 6 | Safety |
| 6 | Safety Management |
| 6 | Rural Health Services |
| 6 | Risk Management |
| 6 | Rhinovirus |
| 6 | Respiratory Syncytial Viruses |
| 6 | Residential Facilities |
| 6 | Quality of Life |
| 6 | Policy Making |
| 6 | Obesity |
| 6 | Motivation |
| 6 | Models, Economic |
| 6 | Measles |
| 6 | Mass Media |
| 6 | Inuits |
| 6 | Infectious Disease Transmission, Professional-to-Patient |
| 6 | Hong Kong |
| 6 | History, 19th Century |
| 6 | Health Resources |
| 6 | Health Care Costs |
| 6 | Guidelines as Topic |
| 6 | Geography |
| 6 | Geese |
| 6 | Fever |
| 6 | Dogs |
| 6 | Diphtheria-Tetanus-Pertussis Vaccine |
| 6 | Cough |
| 6 | Community Health Services |
| 6 | Common Cold |
| 6 | Charadriiformes |
| 6 | Bird Diseases |
| 6 | Animal Husbandry |
| 6 | Aging |
| 6 | Advisory Committees |
| 5 | Volunteers |
| 5 | Virus Shedding |
| 5 | Vaccines |
| 5 | Tertiary Care Centers |
| 5 | Temperature |
| 5 | Social Class |
| 5 | Sequence Homology |
| 5 | Self Report |
| 5 | Resource Allocation |
| 5 | Research Design |
| 5 | Recurrence |
| 5 | Quality of Health Care |
| 5 | Primary Prevention |
| 5 | Population Density |
| 5 | Poisson Distribution |
| 5 | Pediatrics |
| 5 | Outpatients |
| 5 | Organizational Case Studies |
| 5 | Occupational Exposure |
| 5 | Nursing Staff, Hospital |
| 5 | Nose |
| 5 | North America |
| 5 | Narcolepsy |
| 5 | Morbidity |
| 5 | Molecular Diagnostic Techniques |
| 5 | Microbial Sensitivity Tests |
| 5 | Meningococcal Infections |
| 5 | Immunoglobulin G |
| 5 | Hospital Mortality |
| 5 | Heart Diseases |
| 5 | Health Plan Implementation |
| 5 | Haemophilus Vaccines |
| 5 | Guillain-Barre Syndrome |
| 5 | Feasibility Studies |
| 5 | Extracorporeal Membrane Oxygenation |
| 5 | Epitopes |
| 5 | Epidemiology |
| 5 | Enzyme Inhibitors |
| 5 | Environmental Monitoring |
| 5 | England |
| 5 | Electronic Data Processing |
| 5 | Double-Blind Method |
| 5 | Decision Support Techniques |
| 5 | Data Interpretation, Statistical |
| 5 | Cytokines |
| 5 | Cross Protection |
| 5 | Community Pharmacy Services |
| 5 | Cloaca |
| 5 | Clinical Competence |
| 5 | Chickenpox |
| 5 | Cause of Death |
| 5 | Cardiovascular Diseases |
| 5 | Bacterial Infections |
| 5 | Antibody Formation |
| 5 | Anaphylaxis |
| 5 | Ambulatory Care Facilities |
| 5 | Adverse Drug Reaction Reporting Systems |
| 4 | Weather |
| 4 | Vulnerable Populations |
| 4 | Virus Replication |
| 4 | Viral Vaccines |
| 4 | Vaccines, Conjugate |
| 4 | Vaccination Coverage |
| 4 | Trust |
| 4 | Treatment Refusal |
| 4 | Telemedicine |
| 4 | Stress, Psychological |
| 4 | Streptococcal Infections |
| 4 | Sports |
| 4 | Societies, Medical |
| 4 | Sick Leave |
| 4 | Sequence Homology, Amino Acid |
| 4 | Rubella |
| 4 | Respiratory Syncytial Virus, Human |
| 4 | Respiratory Insufficiency |
| 4 | Respiratory Distress Syndrome, Adult |
| 4 | Reminder Systems |
| 4 | Regional Medical Programs |
| 4 | Referral and Consultation |
| 4 | Reagent Kits, Diagnostic |
| 4 | Radiography |
| 4 | Quality-Adjusted Life Years |
| 4 | Public Health Nursing |
| 4 | Program Development |
| 4 | Professional-Patient Relations |
| 4 | Professional Role |
| 4 | Probability |
| 4 | Prenatal Care |
| 4 | Population Dynamics |
| 4 | Placebos |
| 4 | Physician's Role |
| 4 | Pharynx |
| 4 | Perception |
| 4 | Patient Participation |
| 4 | Patient Isolation |
| 4 | Parainfluenza Virus 1, Human |
| 4 | Occupational Health Services |
| 4 | Nunavut |
| 4 | New Zealand |
| 4 | New Brunswick |
| 4 | Multiplex Polymerase Chain Reaction |
| 4 | Moral Obligations |
| 4 | Molecular Epidemiology |
| 4 | Likelihood Functions |
| 4 | Kidney Transplantation |
| 4 | Japan |
| 4 | Intensive Care Units, Pediatric |
| 4 | Informed Consent |
| 4 | Influenza A Virus, H3N8 Subtype |
| 4 | Infections |
| 4 | Infant, Small for Gestational Age |
| 4 | Income |
| 4 | Immunocompromised Host |
| 4 | Immunization, Secondary |
| 4 | Humidity |
| 4 | Hepatitis B |
| 4 | Healthy Volunteers |
| 4 | Healthcare Disparities |
| 4 | Health Care Rationing |
| 4 | France |
| 4 | Ferrets |
| 4 | Federal Government |
| 4 | Epidemiologic Methods |
| 4 | Environmental Exposure |
| 4 | Emigrants and Immigrants |
| 4 | Educational Status |
| 4 | Drug Administration Schedule |
| 4 | Documentation |
| 4 | Disease Susceptibility |
| 4 | DNA Primers |
| 4 | Contact Tracing |
| 4 | Consumer Health Information |
| 4 | Coinfection |
| 4 | Chi-Square Distribution |
| 4 | Cattle |
| 4 | Cats |
| 4 | Catchment Area, Health |
| 4 | Bronchodilator Agents |
| 4 | Bias |
