keywords 2 Aetiology 2.1 Biological and endogenous factors 2.2 Factors relating to the physical environment 32 Biomedical and Clinical Sciences 3207 Medical Microbiology Autoimmune Disease Biodefense Digestive Diseases Emerging Infectious Diseases Infection Infectious Diseases Inflammatory Bowel Disease Inflammatory and immune system Nutrition Oral and gastrointestinal Prevention Vaccine Related