Host Microbe Interaction and Immunology Notes

Host-Microbe Interaction and Immunology Notes

Types of Infection

• Clinical: Infections with signs and symptoms.
• Subclinical: Infection with pathogen but no symptoms.
• Localized: Infection confined to one area of the body.
• Systemic: Infection spread to different areas of the body.
• Iatrogenic (Nosocomial): Infections arising from medical procedures or interventions (e.g., in hospitals).
• Exogenous: Infections originating from the external environment.
• Endogenous: Infections originating from within the human host, including congenital diseases transmitted from mother to fetus.

Modes of Disease Transmission

• Contact Transmission: Direct and indirect physical contact.
• Common Vehicle Transmission: Transmission via airborne particles, food-borne, or water-borne sources.
• Vectors: Organisms, such as insects, that transmit pathogens (mechanical and biological).
• Direct Inoculation: Through means such as parenteral routes (injections).
• Intra-placental: Transmission from mother to fetus through the placenta.

Specific Routes of Infection

• Respiratory-Salivary Route:

  • Droplets: Coughing and sneezing can propel droplets that contain pathogens.
  • Soil-Dust & Water Aerosols: Can also carry pathogenic microbes.

• Oral-Faecal Route:

  • Personal Contact: Direct personal interactions or indirect routes via food/water.

• Sexual Transmission: Interaction between genital regions that can facilitate the spread of STDs.

• Injection Drug Use:

  • Involves sharing needles or syringes that may be contaminated with pathogens.

• Zoonoses: Diseases transmitted from animals to humans directly or via vectors.

Reservoirs of Infectious Agents

• Animate Reservoirs:
  • Includes carriers of the disease who may exhibit healthy or active disease states.
• Inanimate Reservoirs:
  • Includes environmental sources like air, dust, soil, and food.

Epidemiology

• Definition: Study of spread, frequency, and distribution of diseases in populations.
  • Descriptive Epidemiology: Data related to the location, age, time, and occupation to identify patterns in disease spread.
  • Analytical Epidemiology: In-depth investigation to identify causes, transmission modes, and prevention methods.

Classification of Diseases

• Endemic: Constantly present in a population.
• Epidemic: Sudden increase in disease cases within a region.
• Pandemic: Global spread of an epidemic.
• Sporadic: Occasional, irregular occurrences of disease.

Important Terms in Epidemiology

• Aetiology: The cause of a disease.
• Outbreak: Occurrence of disease cases greater than expected in a certain time and place.
• Morbidity: Rate of disease within a population.
• Mortality: Rate of death caused by disease.
• Incidence: Number of new cases within a specified period.
• Prevalence: Total number of specific cases at a given time, both old and new.

Historical Case Study: Dr. John Snow

• Investigated the cholera outbreak in London (1854).
• Mapped cases and traced them to a contaminated water pump, leading to public health actions that halted the outbreak.

Control of Epidemic Diseases

• Preventing Water Contamination:
  • Ensuring clean water treatment and sewage disposal.
• Public Health Education:
  • Teaching communities about infection prevention practices.
• Immunization Programs:
  • Development and distribution of vaccines.
• Isolation of Infected Individuals:
  • Keeping contagious individuals apart from the healthy population.

Immune System Overview

• Immunology: Study of the immune system's components and functions against infectious agents and cancers.
• Innate Immunity: Non-specific defenses present from birth.
• Adaptive Immunity: Specific responses based on prior exposure to antigens.
  • Humoral Immunity: Mediated by B cells producing antibodies.
  • Cell-Mediated Immunity: Involves T cells targeting infected cells.

Inflammation Responses

• Definition: Body's response to injury or infection.
• Effects: Prevention of pathogen spread, removal of debris, and tissue repair.
  • Cardinal Signs: Redness, heat, swelling, pain.

Phagocytosis

• Process by which certain immune cells (like neutrophils and macrophages) engulf and destroy pathogens.

Antibodies

• Structure: Comprised of heavy and light chains forming a Y-shape.
• Function: Bind to antigens and mark them for destruction or neutralization.
  • Isotypes: IgM (initial response), IgG (secondary response), etc.

Vaccination

• Historical practices and modern applications trace back to the prevention of infectious diseases by inducing immunity.
  • Active Immunity: The body produces its own antibodies after exposure.
  • Passive Immunity: Antibodies are provided from external sources;

Autoimmune Diseases

• Occur when the immune system targets the body's own tissues, sometimes triggered by infections due to molecular mimicry.

Summary Questions

1. Different types of infections.
2. Modes of disease transmission.
3. Historical significance of John Snow in epidemiology.
4. Differences between morbidity and mortality, incidence and prevalence.
5. Innate vs. adaptive immunity, their cells, and functions.