| 344 | Humans (MeSH) |
| 236 | Brazil (epidemiology) |
| 221 | Female (MeSH) |
| 200 | Male (MeSH) |
| 149 | Brazil (MeSH) |
| 148 | Influenza, Human (epidemiology) |
| 146 | Middle Aged (MeSH) |
| 144 | Adult (MeSH) |
| 115 | Child, Preschool (MeSH) |
| 110 | Adolescent (MeSH) |
| 106 | Aged (MeSH) |
| 103 | Infant (MeSH) |
| 101 | Child (MeSH) |
| 90 | Influenza, Human (prevention & control) |
| 78 | Young Adult (MeSH) |
| 60 | Seasons (MeSH) |
| 60 | Influenza, Human (virology) |
| 54 | Animals (MeSH) |
| 54 | Aged, 80 and over (MeSH) |
| 53 | Influenza Vaccines (administration & dosage) |
| 52 | Influenza A Virus, H1N1 Subtype (MeSH) |
| 50 | Infant, Newborn (MeSH) |
| 46 | Cross-Sectional Studies (MeSH) |
| 44 | Pandemics (MeSH) |
| 37 | Respiratory Tract Infections (epidemiology) |
| 34 | Risk Factors (MeSH) |
| 34 | Respiratory Tract Infections (virology) |
| 33 | Prospective Studies (MeSH) |
| 30 | Influenza, Human (mortality) |
| 29 | Socioeconomic Factors (MeSH) |
| 29 | Prevalence (MeSH) |
| 29 | Pregnancy (MeSH) |
| 29 | Incidence (MeSH) |
| 28 | Influenza A virus (isolation & purification) |
| 28 | Influenza A Virus, H1N1 Subtype (isolation & purification) |
| 26 | Vaccination (statistics & numerical data) |
| 26 | Time Factors (MeSH) |
| 24 | Orthomyxoviridae Infections (veterinary) |
| 24 | Age Distribution (MeSH) |
| 22 | Phylogeny (MeSH) |
| 22 | Orthomyxoviridae Infections (epidemiology) |
| 22 | Disease Outbreaks (MeSH) |
| 21 | Retrospective Studies (MeSH) |
| 21 | Influenza Vaccines (immunology) |
| 21 | Hospitalization (MeSH) |
| 20 | Reverse Transcriptase Polymerase Chain Reaction (MeSH) |
| 20 | Influenza A Virus, H1N1 Subtype (genetics) |
| 20 | Antibodies, Viral (blood) |
| 20 | Acute Disease (MeSH) |
| 19 | Influenza, Human (diagnosis) |
| 19 | Influenza A Virus, H1N1 Subtype (immunology) |
| 18 | Influenza, Human (immunology) |
| 18 | Influenza Vaccines (adverse effects) |
| 18 | Hemagglutination Inhibition Tests (MeSH) |
| 17 | Vaccination (MeSH) |
| 17 | Orthomyxoviridae Infections (virology) |
| 17 | Hospitalization (statistics & numerical data) |
| 16 | Severity of Illness Index (MeSH) |
| 16 | Influenza, Human (drug therapy) |
| 15 | Swine (MeSH) |
| 15 | Respiratory Syncytial Virus Infections (epidemiology) |
| 15 | Antiviral Agents (therapeutic use) |
| 15 | Age Factors (MeSH) |
| 14 | Swine Diseases (virology) |
| 14 | Population Surveillance (MeSH) |
| 13 | Swine Diseases (epidemiology) |
| 13 | Influenza, Human (history) |
| 13 | Influenza, Human (complications) |
| 13 | Influenza Vaccines (MeSH) |
| 13 | Influenza B virus (isolation & purification) |
| 13 | Influenza A virus (genetics) |
| 13 | History, 20th Century (MeSH) |
| 13 | Cohort Studies (MeSH) |
| 12 | Urban Population (MeSH) |
| 12 | RNA, Viral (genetics) |
| 12 | Pandemics (prevention & control) |
| 12 | Influenza, Human (transmission) |
| 12 | Epidemiological Monitoring (MeSH) |
| 11 | Virus Diseases (epidemiology) |
| 11 | Influenza Vaccines (therapeutic use) |
| 11 | Influenza A virus (immunology) |
| 10 | Sequence Analysis, DNA (MeSH) |
| 10 | Pandemics (statistics & numerical data) |
| 10 | Oseltamivir (therapeutic use) |
| 10 | Molecular Sequence Data (MeSH) |
| 10 | Influenza B virus (genetics) |
| 10 | Comorbidity (MeSH) |
| 9 | Treatment Outcome (MeSH) |
| 9 | Sex Distribution (MeSH) |
| 9 | Pneumonia, Viral (epidemiology) |
| 9 | Orthomyxoviridae (immunology) |
| 9 | Neuraminidase (genetics) |
| 9 | Influenza, Human (microbiology) |
| 9 | Influenza A virus (classification) |
| 9 | Hemagglutinin Glycoproteins, Influenza Virus (genetics) |
| 9 | Fluorescent Antibody Technique, Indirect (MeSH) |
| 9 | Community-Acquired Infections (epidemiology) |
| 8 | Virus Diseases (virology) |
| 8 | Seroepidemiologic Studies (MeSH) |
| 8 | Rhinovirus (isolation & purification) |
| 8 | Respiratory Syncytial Virus, Human (isolation & purification) |
| 8 | Nasopharynx (virology) |
| 8 | Influenza, Human (therapy) |
| 8 | Influenza A Virus, H3N2 Subtype (isolation & purification) |
| 8 | Coinfection (epidemiology) |
| 7 | Vaccination (adverse effects) |
| 7 | Tropical Climate (MeSH) |
| 7 | Surveys and Questionnaires (MeSH) |
| 7 | Sentinel Surveillance (MeSH) |
| 7 | Respiratory Tract Infections (mortality) |
| 7 | Respiratory Syncytial Viruses (isolation & purification) |
| 7 | Real-Time Polymerase Chain Reaction (MeSH) |
| 7 | Pregnancy Complications, Infectious (epidemiology) |
| 7 | Models, Biological (MeSH) |
| 7 | Mice (MeSH) |
| 7 | Logistic Models (MeSH) |
| 7 | Influenza A Virus, H1N1 Subtype (drug effects) |
| 7 | Health Status (MeSH) |
| 7 | Health Personnel (MeSH) |
| 7 | Health Knowledge, Attitudes, Practice (MeSH) |
| 7 | Genetic Variation (MeSH) |
| 7 | Disease Outbreaks (history) |
| 7 | Coinfection (virology) |
| 6 | Viruses (isolation & purification) |
| 6 | Statistics, Nonparametric (MeSH) |
| 6 | Sex Factors (MeSH) |
| 6 | Risk Assessment (MeSH) |
| 6 | Rhinovirus (genetics) |
| 6 | Respiratory Tract Infections (prevention & control) |
| 6 | Respiratory Syncytial Virus Infections (virology) |
| 6 | Public Health (MeSH) |
| 6 | Population Surveillance (methods) |
| 6 | Pneumonia, Viral (diagnosis) |
| 6 | Picornaviridae Infections (epidemiology) |
| 6 | Paramyxoviridae Infections (epidemiology) |
| 6 | Orthomyxoviridae (isolation & purification) |
| 6 | Multivariate Analysis (MeSH) |
| 6 | Influenza, Human (economics) |
| 6 | Influenza B virus (classification) |
| 6 | Immunization Programs (MeSH) |
| 6 | Horses (MeSH) |
| 6 | Horse Diseases (epidemiology) |
| 6 | Epidemics (MeSH) |
| 6 | Coronavirus Infections (epidemiology) |
| 6 | Case-Control Studies (MeSH) |
| 6 | Adenoviridae (isolation & purification) |
| 5 | Viruses (classification) |
| 5 | Viral Load (MeSH) |
| 5 | Travel (MeSH) |
| 5 | Tetanus Toxoid (administration & dosage) |
| 5 | Respiratory Tract Diseases (mortality) |
| 5 | Regression Analysis (MeSH) |
| 5 | RNA, Viral (isolation & purification) |
| 5 | RNA, Viral (analysis) |
| 5 | Polymerase Chain Reaction (MeSH) |
| 5 | Pneumonia (mortality) |
| 5 | Pneumococcal Vaccines (administration & dosage) |
| 5 | Orthomyxoviridae Infections (diagnosis) |
| 5 | Mutation (MeSH) |
| 5 | Lung (virology) |
| 5 | Influenza, Human (pathology) |
| 5 | Influenza in Birds (virology) |
| 5 | Influenza in Birds (epidemiology) |
| 5 | Influenza Vaccines (economics) |
| 5 | Influenza B virus (immunology) |
| 5 | Influenza A Virus, H3N2 Subtype (immunology) |
| 5 | Influenza A Virus, H1N1 Subtype (pathogenicity) |
| 5 | Influenza A Virus, H1N1 Subtype (classification) |
| 5 | Immunization Schedule (MeSH) |
| 5 | Hospitals, University (MeSH) |
| 5 | Health Surveys (MeSH) |
| 5 | Genotype (MeSH) |
| 5 | Genome, Viral (MeSH) |
| 5 | Coronavirus Infections (diagnosis) |
| 5 | Community-Acquired Infections (virology) |
| 5 | Chronic Disease (MeSH) |
| 5 | Chi-Square Distribution (MeSH) |
| 5 | Birds (MeSH) |
| 5 | Betacoronavirus (MeSH) |
| 5 | Animal Migration (MeSH) |
| 4 | Viruses (genetics) |
| 4 | Viral Proteins (genetics) |
| 4 | Vaccination (psychology) |
| 4 | Tetanus Toxoid (immunology) |
| 4 | Spatio-Temporal Analysis (MeSH) |
| 4 | Serologic Tests (MeSH) |
| 4 | Sensitivity and Specificity (MeSH) |
| 4 | Risk (MeSH) |
| 4 | Respiratory Tract Infections (microbiology) |
| 4 | Respiratory Tract Infections (etiology) |
| 4 | Respiratory Tract Infections (diagnosis) |
| 4 | Respiratory Tract Diseases (epidemiology) |
| 4 | Respiratory Syncytial Viruses (genetics) |
| 4 | Prognosis (MeSH) |
| 4 | Pneumonia, Viral (virology) |
| 4 | Paramyxoviridae Infections (virology) |
| 4 | Orthomyxoviridae (MeSH) |
| 4 | Nasal Lavage Fluid (virology) |
| 4 | Morbidity (MeSH) |
| 4 | Molecular Epidemiology (MeSH) |
| 4 | Models, Statistical (MeSH) |
| 4 | Metapneumovirus (isolation & purification) |
| 4 | Mass Vaccination (statistics & numerical data) |
| 4 | Mass Vaccination (MeSH) |
| 4 | Influenza A Virus, H1N2 Subtype (isolation & purification) |
| 4 | Indians, South American (MeSH) |
| 4 | Hospitals, University (statistics & numerical data) |
| 4 | Hospital Mortality (MeSH) |
| 4 | Health Promotion (MeSH) |
| 4 | Haemophilus Vaccines (immunology) |
| 4 | Haemophilus Vaccines (administration & dosage) |
| 4 | HIV Infections (complications) |
| 4 | Gestational Age (MeSH) |
| 4 | Epidemiologic Methods (MeSH) |
| 4 | Disease Outbreaks (veterinary) |
| 4 | Disease Notification (MeSH) |
| 4 | Databases, Factual (MeSH) |
| 4 | Cross Infection (prevention & control) |
| 4 | Cost-Benefit Analysis (MeSH) |
| 4 | Bird Diseases (epidemiology) |
| 4 | Argentina (epidemiology) |
| 4 | Antigens, Viral (analysis) |
| 4 | Antibodies, Viral (immunology) |
| 4 | Antibodies, Viral (analysis) |
| 4 | Antibodies, Bacterial (blood) |
| 4 | Adenovirus Infections, Human (epidemiology) |
| 4 | Adenoviridae Infections (epidemiology) |
| 3 | Zika Virus Infection (epidemiology) |
| 3 | Virus Diseases (prevention & control) |
| 3 | Vaccines, Conjugate (administration & dosage) |
| 3 | Vaccination Coverage (statistics & numerical data) |
| 3 | Vaccination (standards) |
| 3 | Vaccination (methods) |
| 3 | United States (MeSH) |
| 3 | Tertiary Care Centers (MeSH) |
| 3 | Swine Diseases (prevention & control) |
| 3 | Students, Medical (statistics & numerical data) |
| 3 | South Africa (epidemiology) |
| 3 | Ships (MeSH) |
| 3 | Self Report (MeSH) |
| 3 | Reverse Transcriptase Polymerase Chain Reaction (methods) |
| 3 | Respirovirus (isolation & purification) |
| 3 | Respiratory Tract Diseases (etiology) |
| 3 | Respiratory Syncytial Virus Infections (diagnosis) |
| 3 | Public Health Surveillance (MeSH) |
| 3 | Program Evaluation (MeSH) |
| 3 | Pregnancy Outcome (epidemiology) |
| 3 | Pregnancy Complications, Infectious (prevention & control) |
| 3 | Pregnancy Complications, Infectious (drug therapy) |
| 3 | Poisson Distribution (MeSH) |
| 3 | Pneumonia, Viral (prevention & control) |
| 3 | Pneumonia, Bacterial (epidemiology) |
| 3 | Pneumonia (epidemiology) |
| 3 | Picornaviridae Infections (virology) |
| 3 | Patient Compliance (statistics & numerical data) |
| 3 | Parainfluenza Virus 3, Human (isolation & purification) |
| 3 | Pandemics (history) |
| 3 | Oseltamivir (pharmacology) |
| 3 | Orthomyxoviridae Infections (prevention & control) |
| 3 | Orthomyxoviridae (classification) |
| 3 | Metapneumovirus (genetics) |
| 3 | Maternal Mortality (MeSH) |
| 3 | Lung (pathology) |
| 3 | Longitudinal Studies (MeSH) |
| 3 | Influenza, Human (genetics) |
| 3 | Influenza, Human (etiology) |
| 3 | Influenza, Human (MeSH) |
| 3 | Influenza A virus (MeSH) |
| 3 | Influenza A Virus, H3N8 Subtype (immunology) |
| 3 | Influenza A Virus, H3N2 Subtype (genetics) |
| 3 | Influenza A Virus, H1N2 Subtype (genetics) |
| 3 | Influenza A Virus, H1N1 Subtype (physiology) |
| 3 | Immunosuppressive Agents (therapeutic use) |
| 3 | Immunization Programs (statistics & numerical data) |
| 3 | Immunization Programs (standards) |
| 3 | Hospitals, Teaching (MeSH) |
| 3 | Horse Diseases (virology) |
| 3 | Hemagglutination Tests (MeSH) |
| 3 | Health Services for the Aged (statistics & numerical data) |
| 3 | Health Services for the Aged (MeSH) |
| 3 | Health Personnel (statistics & numerical data) |
| 3 | Haemophilus influenzae type b (immunology) |
| 3 | HIV Infections (drug therapy) |
| 3 | Guideline Adherence (MeSH) |
| 3 | Follow-Up Studies (MeSH) |
| 3 | Fatal Outcome (MeSH) |
| 3 | Educational Status (MeSH) |
| 3 | Drug Resistance, Viral (genetics) |
| 3 | Dogs (MeSH) |
| 3 | Disease Transmission, Infectious (prevention & control) |
| 3 | Disease Outbreaks (statistics & numerical data) |
| 3 | Disease Outbreaks (prevention & control) |
| 3 | Dengue (epidemiology) |
| 3 | Death Certificates (MeSH) |
| 3 | Cross Infection (epidemiology) |
| 3 | Coronavirus Infections (prevention & control) |
| 3 | Community-Acquired Infections (microbiology) |
| 3 | Cluster Analysis (MeSH) |
| 3 | Chile (epidemiology) |
| 3 | Chick Embryo (MeSH) |
| 3 | Cause of Death (trends) |
| 3 | CD4 Lymphocyte Count (MeSH) |
| 3 | Australia (epidemiology) |
| 3 | Attitude to Health (MeSH) |
| 3 | Attitude of Health Personnel (MeSH) |
| 3 | Antiviral Agents (pharmacology) |
| 3 | Animals, Wild (MeSH) |
| 3 | Animal Husbandry (MeSH) |
| 3 | Amino Acid Substitution (MeSH) |
| 3 | Adenoviruses, Human (isolation & purification) |
| 3 | Adenovirus Infections, Human (virology) |
| 3 | Absenteeism (MeSH) |
| 2 | Zika Virus Infection (virology) |
| 2 | Zika Virus (isolation & purification) |
| 2 | Weight Loss (MeSH) |
| 2 | Virus Diseases (mortality) |
| 2 | Virus Diseases (diagnosis) |
| 2 | Virus Cultivation (MeSH) |
| 2 | Virulence Factors (genetics) |
| 2 | Vaccines, Inactivated (immunology) |
| 2 | Vaccines, Inactivated (adverse effects) |
| 2 | Vaccines, Conjugate (immunology) |
| 2 | Vaccines, Combined (immunology) |
| 2 | Vaccines, Combined (MeSH) |
| 2 | Vaccines (adverse effects) |
| 2 | Vaccination (trends) |
| 2 | Vaccination (economics) |
| 2 | Urban Population (statistics & numerical data) |
| 2 | United States (epidemiology) |
| 2 | United Kingdom (MeSH) |
| 2 | USSR (MeSH) |
| 2 | Treatment Refusal (MeSH) |
| 2 | Temperature (MeSH) |
| 2 | Technology Transfer (MeSH) |
| 2 | Swine Diseases (diagnosis) |
| 2 | Sus scrofa (MeSH) |
| 2 | Severe Acute Respiratory Syndrome (virology) |
| 2 | Severe Acute Respiratory Syndrome (epidemiology) |
| 2 | Serotyping (MeSH) |
| 2 | Sequence Deletion (MeSH) |
| 2 | Sequence Analysis (MeSH) |
| 2 | Sanitation (history) |
| 2 | Rural Population (MeSH) |
| 2 | Rhinovirus (classification) |
| 2 | Rhinovirus (MeSH) |
| 2 | Respirovirus (immunology) |
| 2 | Respiratory Tract Infections (veterinary) |
| 2 | Respiratory Tract Infections (physiopathology) |
| 2 | Respiratory Tract Diseases (prevention & control) |
| 2 | Respiratory Tract Diseases (complications) |
| 2 | Respiratory System (virology) |
| 2 | Respiratory Syncytial Viruses (immunology) |
| 2 | Respiratory Syncytial Virus, Human (genetics) |
| 2 | Respiratory Syncytial Virus Infections (mortality) |
| 2 | Respiratory Sounds (MeSH) |
| 2 | Respiratory Distress Syndrome, Adult (virology) |
| 2 | Respiratory Distress Syndrome, Adult (epidemiology) |
| 2 | Reproducibility of Results (MeSH) |
| 2 | Referral and Consultation (MeSH) |
| 2 | Receptors, CCR5 (genetics) |
| 2 | RNA, Viral (blood) |
| 2 | Quality-Adjusted Life Years (MeSH) |
| 2 | Public Health (history) |
| 2 | Prenatal Care (MeSH) |
| 2 | Pregnant Women (MeSH) |
| 2 | Pregnancy Complications, Infectious (mortality) |
| 2 | Pregnancy Complications, Infectious (MeSH) |
| 2 | Polymorphism, Single Nucleotide (MeSH) |
| 2 | Polymorphism, Genetic (MeSH) |
| 2 | Polymerase Chain Reaction (methods) |
| 2 | Politics (MeSH) |
| 2 | Pneumonia, Viral (transmission) |
| 2 | Pneumonia, Pneumococcal (prevention & control) |
| 2 | Pneumonia, Bacterial (microbiology) |
| 2 | Pneumonia (etiology) |
| 2 | Pneumococcal Infections (prevention & control) |
| 2 | Plant Extracts (pharmacology) |
| 2 | Phylogeography (MeSH) |
| 2 | Patient Compliance (MeSH) |
| 2 | Patient Acceptance of Health Care (statistics & numerical data) |
| 2 | Patient Acceptance of Health Care (MeSH) |
| 2 | Paramyxoviridae Infections (immunology) |
| 2 | Parainfluenza Virus 2, Human (isolation & purification) |
| 2 | Oropharynx (virology) |
| 2 | Odds Ratio (MeSH) |
| 2 | Occupational Diseases (prevention & control) |
| 2 | Nucleic Acid Denaturation (MeSH) |
| 2 | Nose (virology) |
| 2 | New Zealand (epidemiology) |
| 2 | Nasopharynx (microbiology) |
| 2 | Myocardial Ischemia (mortality) |
| 2 | Mycoplasma hyopneumoniae (isolation & purification) |
| 2 | Mutation (genetics) |
| 2 | Mortality (trends) |
| 2 | Mortality (MeSH) |
| 2 | Military Personnel (statistics & numerical data) |
| 2 | Military Personnel (history) |
| 2 | Microscopy, Electron (MeSH) |
| 2 | Microcephaly (epidemiology) |
| 2 | Methods (MeSH) |
| 2 | Meteorological Concepts (MeSH) |
| 2 | Meningitis, Haemophilus (prevention & control) |
| 2 | Meningitis, Haemophilus (epidemiology) |
| 2 | Mass Vaccination (standards) |
| 2 | Mass Vaccination (methods) |
| 2 | Mass Screening (MeSH) |
| 2 | Lupus Erythematosus, Systemic (immunology) |
| 2 | Lupus Erythematosus, Systemic (drug therapy) |
| 2 | Life Style (MeSH) |
| 2 | Length of Stay (MeSH) |
| 2 | Kidney Transplantation (MeSH) |
| 2 | Internationality (MeSH) |
| 2 | Intensive Care Units, Pediatric (MeSH) |
| 2 | Intensive Care Units (statistics & numerical data) |
| 2 | Intensive Care Units (MeSH) |
| 2 | Information Dissemination (MeSH) |
| 2 | Influenza Vaccines (supply & distribution) |
| 2 | Influenza A virus (physiology) |
| 2 | Influenza A Virus, H7N7 Subtype (immunology) |
| 2 | Influenza A Virus, H3N2 Subtype (classification) |
| 2 | Influenza A Virus, H1N2 Subtype (classification) |
| 2 | Infectious Disease Transmission, Professional-to-Patient (prevention & control) |
| 2 | Infections (epidemiology) |
| 2 | Infection Control (methods) |
| 2 | Immunosuppressive Agents (adverse effects) |
| 2 | Immunoglobulin G (blood) |
| 2 | Immunocompromised Host (MeSH) |
| 2 | Hospitals (MeSH) |
| 2 | Horse Diseases (diagnosis) |
| 2 | Hepatitis B (prevention & control) |
| 2 | Hemorrhagic Fever, Ebola (epidemiology) |
| 2 | Hemagglutinin Glycoproteins, Influenza Virus (immunology) |
| 2 | Hemagglutination Inhibition Tests (veterinary) |
| 2 | Health Status Indicators (MeSH) |
| 2 | Health Policy (economics) |
| 2 | Health Behavior (MeSH) |
| 2 | Haemophilus influenzae (physiology) |
| 2 | Haemophilus influenzae (immunology) |
| 2 | Haemophilus Infections (prevention & control) |
| 2 | Haemophilus Infections (immunology) |
| 2 | HIV Infections (epidemiology) |
| 2 | Global Health (MeSH) |
| 2 | Geriatric Assessment (statistics & numerical data) |
| 2 | Geography, Medical (MeSH) |
| 2 | Geography (MeSH) |
| 2 | Genetic Predisposition to Disease (MeSH) |
| 2 | Fourier Analysis (MeSH) |
| 2 | Fluorescent Antibody Technique (MeSH) |
| 2 | Fever (epidemiology) |
| 2 | Farms (MeSH) |
| 2 | Ethnic Groups (MeSH) |
| 2 | Enzyme-Linked Immunosorbent Assay (MeSH) |
| 2 | Emergency Service, Hospital (statistics & numerical data) |
| 2 | Drug Resistance, Viral (drug effects) |
| 2 | Double-Blind Method (MeSH) |
| 2 | Dose-Response Relationship, Immunologic (MeSH) |
| 2 | Disease Susceptibility (MeSH) |
| 2 | Disease Progression (MeSH) |
| 2 | Disease Outbreaks (epidemiology) |
| 2 | Decision Support Techniques (MeSH) |
| 2 | Data Collection (MeSH) |
| 2 | Cross Infection (virology) |
| 2 | Coronavirus Infections (virology) |
| 2 | Coronavirus Infections (transmission) |
| 2 | Coronavirus (isolation & purification) |
| 2 | Coronavirus (genetics) |
| 2 | Complement Fixation Tests (MeSH) |
| 2 | Coinfection (MeSH) |
| 2 | Clinical Laboratory Techniques (methods) |
| 2 | Clinical Laboratory Techniques (MeSH) |
| 2 | Climate (MeSH) |
| 2 | Charadriiformes (virology) |
| 2 | Cerebrovascular Disorders (mortality) |
| 2 | Cerebrospinal Fluid (virology) |
| 2 | Cell Line (MeSH) |
| 2 | Cell Culture Techniques (MeSH) |
| 2 | Cause of Death (MeSH) |
| 2 | Carrier State (microbiology) |
| 2 | Bronchoalveolar Lavage Fluid (virology) |
| 2 | Bronchiolitis (virology) |
| 2 | Breast Feeding (MeSH) |
| 2 | Brazil (ethnology) |
| 2 | Bird Diseases (virology) |
| 2 | Biomarkers (blood) |
| 2 | Betacoronavirus (isolation & purification) |
| 2 | Base Sequence (MeSH) |
| 2 | Bacterial Vaccines (administration & dosage) |
| 2 | Bacterial Infections (prevention & control) |
| 2 | BCG Vaccine (adverse effects) |
| 2 | Avulavirus Infections (veterinary) |
| 2 | Avulavirus Infections (epidemiology) |
| 2 | Avulavirus (isolation & purification) |
| 2 | Asthma (virology) |
| 2 | Asthma (epidemiology) |
| 2 | Argentina (MeSH) |
| 2 | Antigens, Viral (immunology) |
| 2 | Antibodies, Viral (isolation & purification) |
| 2 | Antibodies (analysis) |
| 2 | Air Pollutants (analysis) |
| 2 | Adverse Drug Reaction Reporting Systems (statistics & numerical data) |
