| 1. | Anatomical barriers | 2. | Physiological barriers |
| 3. | Cellular barriers | 4. | Cytokines |
| I: | are caused by hypersensitivity of the immune system to typically harmless substances in the environment. |
| II: | involve immunoglobulin E antibodies |
| 1. | Pre-pubertal | 2. | Adolescence |
| 3. | Late adulthood | 4. | Geriatric |
| 1. | Know your Status |
| 2. | Communities Make the Difference |
| 3. | Global Solidarity Shared Responsibility |
| 4. | End inequalities. End AIDS. End pandemics. |
| 1. | through sexual contact with an infected person |
| 2. | from mother to child during pregnancy, delivery, or breastfeeding |
| 3. | via blood and blood products |
| 4. | vector borne |
| 1. | Swine flu | 2. | Dengue |
| 3. | Covid-19 | 4. | Avian influenza |