Chain of Transmission

Flashcards:

Q: What is the "chain of transmission"?
A: The process by which infectious diseases spread, consisting of six linked elements.

Q: What are the six links in the chain of transmission?
A:

1. Infectious agent

2. Reservoir

3. Portal of exit

4. Mode of transmission

5. Portal of entry

6. Susceptible host

Q: What is an infectious agent? Give examples.
A: A microorganism capable of causing disease (e.g., bacteria, viruses, fungi, parasites, protozoa).

Q: What is a reservoir? Give examples.
A: The natural environment where the agent lives and multiplies (e.g., surfaces, soil, animals, humans, food, water, body fluids like urine, blood, sweat, tears, respiratory secretions).

Q: What is a portal of exit? Give examples.
A: The path by which the agent leaves the reservoir (e.g., respiratory tract, GI tract, mouth, nose, blood, wounds, mucous membranes, urine, sexual secretions).

Q: What are the modes of transmission?
A:

• Direct: Contact, droplet.

• Indirect: Airborne, vehicle-borne (food, water, objects), vector-borne (mosquitoes, ticks).

Q: What is a portal of entry? Give examples.
A: The way the agent enters the host (e.g., respiratory tract, GI tract, skin, mucous membranes, wounds).

Q: What makes a host susceptible?
A: Weak or compromised immune system (e.g., immunocompromised person, neonates, elderly, cancer patients, wounds, burns, diabetes mellitus, immunosuppressive drugs).

Q: How can infection be prevented in the chain of transmission?
A: Break any link by:

• Eliminating the agent (sterilisation, antibiotics).

• Controlling the reservoir (hygiene, sanitation).

• Blocking portals of exit (PPE, cough etiquette).

• Interrupting transmission (hand hygiene, isolation).

• Protecting portals of entry (wound care, masks).

• Strengthening host defences (vaccination, nutrition, rest).