Chain of Infection: Understanding Disease Transmission

Vector-borne transmission is a type of direct contact.

The reservoir of an infectious agent can be a combination of a person and an environment.

A person with a weakened immune system is not susceptible to infectious agents.

The portal of entry is the route by which an infectious agent leaves a susceptible host.

The respiratory tract is an example of a portal of exit.

The skin is not a possible portal of entry for infectious agents.

Animals can be a reservoir of an infectious agent.

A person with diabetes is not susceptible to infectious agents.

Indirect contact is a type of airborne transmission.

The mucous membranes can serve as a portal of entry for infectious agents.

Humans cannot be a reservoir of an infectious agent.

Vector-borne transmission involves direct contact between two individuals.

The elderly are not more susceptible to infectious agents due to their age.

Contaminated water can be a reservoir of an infectious agent.

The respiratory tract is not a potential portal of entry for infectious agents.

Chain of Infection

The chain of infection is a model used to understand the transmission of infectious diseases. It consists of six elements: reservoir, mode of transmission, susceptible host, portal of entry, portal of exit, and infectious agent.

Reservoir

A reservoir is the natural habitat of an infectious agent
Can be a person, animal, or environment
Examples:
- Humans (e.g., COVID-19)
- Animals (e.g., mosquitoes for malaria)
- Environment (e.g., contaminated water for cholera)

Mode of Transmission

The way an infectious agent is transmitted from the reservoir to a susceptible host
Examples:
- Direct contact (e.g., touching, shaking hands)
- Indirect contact (e.g., contaminated surfaces, fomites)
- Airborne transmission (e.g., respiratory droplets)
- Vector-borne transmission (e.g., mosquitoes, ticks)

Susceptible Host

A person or animal that is not immune to an infectious agent
Factors that increase susceptibility:
- Age (e.g., young, elderly)
- Underlying health conditions (e.g., diabetes, HIV)
- Weakened immune system (e.g., cancer, chemotherapy)

Portal of Entry

The route by which an infectious agent enters a susceptible host
Examples:
- Respiratory tract (e.g., influenza)
- Gastrointestinal tract (e.g., food poisoning)
- Skin (e.g., cuts, wounds)
- Mucous membranes (e.g., eyes, nose, mouth)

Portal of Exit

The route by which an infectious agent leaves a reservoir
Examples:
- Respiratory tract (e.g., coughing, sneezing)
- Gastrointestinal tract (e.g., diarrhea, vomiting)
- Skin (e.g., wounds, skin lesions)
- Mucous membranes (e.g., eyes, nose, mouth)

Learn about the six elements of the chain of infection model, including reservoir, mode of transmission, susceptible host, portal of entry, portal of exit, and infectious agent. Understand how infectious diseases are transmitted and how to prevent them.