| Element in the cycle of infection | Explanation | Common examples |
| 1. Infectious Agent | When germs enter the body, they can cause illness | - Bacteria, virus, fungi, protozoa
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| 2. Reservoir | Where germs normally live and multiply | - Humans
- Contaminated food, water, toys, sports equipment
- Insects, animals, soil
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| 3. Portal of Exit | How germs leave the body | - Respiratory tract
- Intestinal tract
- Urinary/genitourinary tract
- Open wounds
- Blood and body fluids
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| 4. Transmission | How germs are spread
* Refer to next page for a detailed explanation of how infections spread. | - Direct physical contact
- Respiratory droplet
- Stool (fecal-oral route)
- Contact with blood/body fluids
- Indirect contact
- Needle stick injury
- Ingestion of contaminated food and water
- Contaminated dust particles
- Contaminated objects
- Insects/animals
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| 5. Portal of Entry | How germs enter the body | - Respiratory tract
- Intestinal tract
- Urinary/genitourinary tract
- Open wounds
- Mucus membrane, e.g. eye, mouth
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| 6. Susceptible Host | A person who gets an infection because he/she is unable to successfully fight the infection | - Infants, elderly and debilitated.
- Persons who are ill.
- Children who are not fully immunized or have underdeveloped immune systems.
- Persons taking certain drugs that lower their defenses against germs.
- Persons with underlying disease conditions that lower their defense against other germs.
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