Transmission of Infectious Diseases

Direct Transmission

• Involves physical contact between infected and susceptible individuals.
• Direct Contact Examples:
  • Kissing
  • Skin-to-skin contact
  • Sexual intercourse
• Droplet Spread Mechanisms:
  • Sneezing
  • Coughing
  • Talking

Indirect Transmission

• Transfer of infectious agents without direct human-to-human contact.
• Involves:
  • Airborne particles
  • Contaminated inanimate objects (vehicles)
  • Animate intermediaries like vectors

Zoonosis

• Infectious disease that can be transmitted from animals to humans under normal conditions.

Levels of Disease Occurrence

• Endemic: Ongoing, constant presence of a disease in a specific area.
• Epidemic: Increased occurrence of disease above expected levels in a defined area or group.
• Pandemic: Widespread epidemic affecting multiple countries or continents.

Chain of Infection

• Infectious Agent: Pathogen responsible for disease.
• Reservoir: Habitat (human, animal, or environment) where the infectious agent lives and multiplies.
• Portal of Exit: Route through which the infectious agent exits the reservoir.
• Means of Transmission: Methods by which the pathogen spreads.
• Portal of Entry: Route through which the pathogen enters a new host.
• Susceptible Host: A person or organism that can become infected by the agent.

Carrier

• A person or animal that carries a specific infectious agent without showing symptoms and can transmit it to others.

Host

• Living organism capable of being infected by a specific infectious agent.

Incubation Period

• Time duration from infection to the appearance of disease symptoms.

The Epidemiologic Triangle

• Host Factors: Traits, behaviors, genetic predisposition, and immunologic factors affecting disease likelihood.
• Agents: Biological, physical, or chemical factors necessary for disease development.
• Environment: External physical, biological, or social conditions that influence the disease process.

Morbidity, Pathogenicity, and Virulence

• Morbidity: Any deviation from a state of well-being, either mental or physical.
• Pathogenicity: Rate at which those exposed to a pathogen develop disease.
• Virulence: Severity of disease caused by a microorganism and its ability to invade tissues.

Prevention Concepts

• Primary Prevention:
  • Aim is to prevent diseases before they occur.
  • Strategies include health promotion and education.
• Secondary Prevention:
  • Focuses on early detection and intervention to halt disease progression.
  • Involves health screenings and prompt treatments.
• Tertiary Prevention:
  • Actions taken when a disease is advanced to reduce impacts and promote patient adaptation.
  • Includes rehabilitation and disability limitation efforts.