Infectious Disease Process Overview

Infectious Disease Process

• The study covers the review of modes and mechanisms of transmission of infectious diseases.
• The objectives of the unit include describing the concepts of infection, infectious & infectivity, defining terms related to infection prevention and control, explaining the infectious disease process (chain of infection), and explaining the dynamics of disease transmission.

Natural History

• The natural history of a disease traces its progress in an infected individual, excluding any medical intervention.
• This progression typically follows a pattern from exposure to recovery/disability or death.

Natural History: Phases

• Pre-pathogenesis: The period before disease onset, characterized by favorable conditions for infection.
• Pathogenesis: The active disease phase, lasting until its conclusion.

Definition of Terms

• Infection: The entry and establishment of an infectious agent within a host. Alternatively, it's the presence of a microorganism in host tissue, where it grows, multiplies, inducing an immune response causing signs & symptoms.
• Infectivity: The ability of a microorganism to lodge and multiply successfully within a host.
• Host: A living organism where an infectious agent can reside and reproduce.

Standard Precautions

• Standard precautions are minimum infection prevention practices for all patient care, regardless of their infection status.
• Standard precautions assume everyone has infectious agents in their blood or body fluids
• Elements include hand hygiene, personal protective equipment (PPE), respiratory hygiene (cough etiquette), safe handling of sharps, proper equipment decontamination, and safe laundry/waste management practices.

Universal Precautions

• Universal precautions treat all human blood and body fluids as if they are infected with HIV or other bloodborne pathogens.
• These precautions mandate infection prevention and control measures.

Homework - Terms to Define

• Asepsis: The absence of disease-causing microorganisms.
• Medical asepsis: Maintaining cleanliness to reduce the spread of pathogens.
• Surgical asepsis: Ensuring a completely sterile environment free of microorganisms.
• Aseptic technique: Practices used to maintain an aseptic environment
• Isolation: Separating infected individuals to prevent further transmission.
• Reverse Isolation: A method for protecting immunocompromised patients and others from infection.
• Barrier nursing: Using physical barriers to prevent infection transmission.
• Nosocomial infection: An infection acquired in a hospital or healthcare facility
• Standard precautions: Infection prevention practices applicable to all patient interactions
• Transmission-based precautions: Additional precautions for patients known or suspected to have highly transmissible infections.
• Personal Protective Equipment (PPE): Safety equipment such as gloves and masks to prevent exposure to infections.

Disease Transmission

• Disease transmission is any method through which an infectious agent spreads to or through the environment.

Chain of Infection

• The chain of infection describes stages from an infectious agent, the reservoir, portal of exit, mode of transmission, portal of entry, to a conducive and susceptible host.

Infectious Agent

• An infectious agent is a microorganism (bacteria, virus, fungi, parasites) capable of causing infection.
• The agent's virulence, invasiveness, and pathogenicity determine its potential to cause disease.

Reservoir

• A reservoir is a place where infectious agents thrive and reproduce, including humans, animals, and inanimate objects like water.

Portal of Exit

• A portal of exit is a bodily opening, like the nose, mouth, or sores, through which an infectious agent can leave a reservoir.

Mode of Transmission

• Modes (means) of disease transmission include contact (direct and indirect), droplet, airborne, vector, and common vehicle transmission.

Portal of Entry

• The portal of entry is the way an infectious agent enters a susceptible host (through ingestion, breathing, damaged skin).

Susceptible Host

• A susceptible host lacks immunity or resistance to infection. Compromised immune systems increase the likelihood of infection.

Modes of Transmission: Detailed

• Airborne: Infection spread via dust or particles (<5 microns) dispersed by air currents.
• Droplet: Transmission involving large droplets (≥ 5microns) propelled short distances. These droplets may land directly or indirectly on susceptible hosts or objects.
• Contact: Transmission via direct physical touch or indirect contact via contaminated objects.
• Vector: Transmission involving animals or insects carrying and transmitting the infectious agent.
• Common Vehicle: Transmission involving a shared contaminated source (food, water, medication, or equipment).

Infection Control Measures

• Direct Contact Transmission: Transmission via direct physical contact with an infected individual. Touching, shaking hands, or close proximity interactions can transmit infection.
• Indirect Contact Transmission: Transmission of microorganisms via an object. Touching surfaces containing microorganisms and contaminating other surfaces.

Hand Hygiene

• Hand hygiene is a critical infection control practice focused on cleaning hands before and after patient contact. Five moments for hand hygiene: before and after patient contact, before and after procedure/exposing body fluids, and after touching a patient's surrounding environment.