In-Depth Notes on Disease Categories and Immunity

Overview of Disease Categories

Infectious Diseases

  • Definition: Diseases caused by microorganisms (bacteria, viruses, fungi, parasites) that can be transmitted from one individual to another. Their transmission can be through direct contact, air, or other means.
Examples of Infectious Diseases:

  1. Bacterial Infections:

    • Syphilis: Caused by Treponema Pallidum. Spreads through direct contact, usually sexual. Symptoms include sores on genitals or mouth.
    • Pneumonia: Can be caused by bacteria, viruses, or fungi. Spread through respiratory secretions.
    • Tetanus: Caused by Clostridium tetani. Not transmitted person to person, but through open wounds.
    • Tuberculosis (TB): Caused by Mycobacterium tuberculosis, spread via airborne transmission when an infected person coughs or sneezes.

  2. Fungal Infections:

    • Ringworm: Caused by fungi like Trichophyton. Spread through direct skin-to-skin contact.
    • Athlete's Foot: Caused by dermatophytes, contracted by walking barefoot or through sweaty feet.
    • Yeast Infection: Often caused by Candida albicans. Factors include antibiotic use, diabetes, and weakened immunity.

  3. Protozoan Infections:

    • Malaria: Caused by Plasmodium, transmitted through the bites of infected mosquitoes.

  4. Viral Infections:

    • Chickenpox: Caused by varicella-zoster virus, spread through direct contact with blisters.
    • Smallpox: Caused by variola virus, spread through respiratory droplets.
    • Measles: Transmitted when an infected person coughs or sneezes.
    • Polio: Caused by poliovirus, primarily spreads through the fecal-oral route.

  5. Helminth Infections:

    • Ascariasis: Caused by roundworms, contracted via contaminated soil or water.
    • Taeniasis: Caused by tapeworms, often from consuming undercooked meat infected with larvae.

Non-Infectious Diseases

  • Definition: Diseases not caused by infectious agents, often due to genetic, environmental, or lifestyle factors.
Examples of Non-Infectious Diseases:
  • Cancer: Uncontrolled cell growth, caused by genetic mutations, environmental triggers, and lifestyle factors.
  • Cardiovascular Disease: Includes heart diseases caused by various factors, including diet and exercise.
  • Diabetes: A metabolic disorder characterized by blood sugar regulation problems.
  • Chronic Lung Illnesses: Such as COPD, often caused by smoking or environmental irritants.

Genetic Diseases

  • Definition: Diseases resulting from genetic mutations or chromosomal abnormalities.
Examples of Genetic Diseases:
  1. Single Gene Inheritance: e.g. Sickle Cell Anemia.
  2. Multifactorial Inheritance: e.g. Breast Cancer.
  3. Chromosomal Abnormalities: e.g. Down Syndrome.
  4. Mitochondrial Inheritance: e.g. Myoclonus Epilepsy.

Role of Microorganisms in Infectious Diseases

  • Microorganisms disrupt normal bodily functions, leading to infection.
  • They multiply within the host, causing harm.

Transmission of Infectious Diseases

  • Modes of Transmission:
  1. Person to Person: Direct contact; e.g., bodily fluids, respiratory droplets.
  2. Droplet Transmission: Released from coughs/sneezes, e.g., Influenza.
  3. Airborne Transmission: Pathogens suspended in the air, e.g., Tuberculosis.
  4. Faecal-Oral Transmission: Contaminated food/water, e.g., Cholera.
  5. Bloodborne Transmission: Through blood/body fluids, e.g., HIV.
  6. Contaminated Food and Water: Ingestion leads to spread, e.g., Salmonella.
  7. Mother to Unborn Child: Pathogens cross placenta or during birth, e.g., Rubella.

Factors Increasing Risk of Infectious Diseases

Environmental Factors

  • Poor Sanitation: Linked to waterborne diseases; can be mitigated by improving sanitation.
  • Climate Change: Can expand vector habitats; mitigated through control programs.

Biological Factors

  • Age: Young and elderly have weakened immunity. Vaccination can reduce risks.
  • Immune Deficiencies: Individuals need support to bolster immunity (nutrition, exercise).

Social and Behavioral Factors

  • Unprotected Sex: Increases STI risk. Education and condom use necessary for risk reduction.
  • Poor Health Behaviors: Smoking and alcohol compromise immunity.

Healthcare-Related Factors

  • Access to Healthcare: Limited access increases disease risk; infrastructure improvements needed.
  • Antibiotic Resistance: Overuse leads to resistant strains; responsible prescription practices are necessary.

Advantages and Dangers of Antibiotics

Advantages

  1. Effective Treatment: Targets bacterial infections effectively.
  2. Prevention: Mitigates complications from surgeries/injuries.
  3. Increased Safety: Essential for patients with compromised immunity.

Dangers

  1. Antibiotic Resistance: Overuse leads to ineffectiveness of treatment.
  2. Side Effects: May cause nausea, diarrhea, etc.
  3. Disruption of Beneficial Bacteria: Can harm gut flora.
  4. Allergic Reactions: Some individuals may have severe reactions.

Defense Mechanisms of the Human Body

External Defense Mechanisms

  • Skin: Protects against pathogens directly.
  • Mucous Membranes: Trap pathogens in respiratory and digestive tracts.
  • Tears and Saliva: Contain enzymes (lysozymes) that attack bacteria.
  • Stomach Acid: Kills ingested pathogens.

Internal Defense Mechanisms

  • Inflammation: Attracts immune cells to sites of infection.
  • Phagocytosis: White blood cells (e.g., macrophages) engulf pathogens.
  • Fever: Raises body temperature to inhibit pathogen growth.

Types of Immunity

Natural Active Immunity

  • Formed after exposure to pathogens; long-term protection via memory cells (e.g., chickenpox).

Natural Passive Immunity

  • Antibodies from another person naturally (e.g., maternal antibodies via placenta or breast milk).

Artificial Passive Immunity

  • Introduction of antibodies from an external source for immediate protection (e.g., rabies post-exposure treatments).

Disruptions to the Immune Response

  1. Immunodeficiency Diseases: Impact's body's ability to fight infection (e.g., HIV/AIDS).
  2. Autoimmune Disorders: The immune system attacks healthy tissue (e.g., rheumatoid arthritis).
  3. Hypersensitivity Reactions: Overactive immune responses lead to allergies or anaphylaxis.