Chain of Infection Overview

Chain of Infection

• Infectious Agent: A pathogen (bacteria, viruses, parasites) that causes disease.

• Source of Infection (Host/Reservoir): Can be animate (e.g., animals like bats, pigs, cows) or inanimate objects (e.g., surfaces, medical equipment, food).

• Inanimate Objects: Non-living things that can harbor microorganisms, such as doorknobs and blood pressure cuffs.

Portal of Exit

• The means by which the infectious agent leaves the host, e.g., through vomiting, urine, blood, or stool.

Mode of Transmission

• Direct Contact: Physical transfer from an infected individual to a susceptible host.
• Indirect Contact: Transfer via contaminated objects (e.g., needles, medical instruments).

Portal of Entry

• Means by which microorganisms enter a susceptible host, e.g., through the gastrointestinal tract, respiratory tract, or skin breaks.

Susceptible Host

• An individual likely to contract the disease, often due to weakened immunity (e.g., elderly, trauma patients).

Important Notes

• Each step in the chain of infection is critical to understanding how infections spread.
• Familiarity with terminology is vital for both understanding and examination purposes.