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Health, Disease, and Immunity

Health and Disease​

1. Definition of Health​

WHO Definition:

  • State of complete physical, mental, social well-being
  • Not merely absence of disease/infirmity
  • Holistic approach
  • Includes lifestyle factors

Factors Affecting Health:

  • Genetics (inherited predisposition)
  • Environment (pollution, climate)
  • Lifestyle (diet, exercise, stress)
  • Access to healthcare
  • Socioeconomic status
  • Education and awareness

2. Communicable Diseases (संचारी रोग)​

Definition:

  • Caused by pathogens (disease-causing organisms)
  • Spread from person to person
  • Can be controlled by breaking transmission chain

Pathogens (रोगजनक):

  • Bacteria: Single-celled prokaryotes

    • Example: Tuberculosis (TB), pneumonia
    • Produce toxins or cause inflammation

  • Viruses: Obligate intracellular parasites

    • Require host cell for reproduction
    • Example: HIV, influenza, COVID-19
    • No cure (vaccines preventive)

  • Fungi: Eukaryotic organisms

    • Example: Athlete's foot, ringworm
    • Slow growth and spread

  • Protoctists/Parasites: Larger organisms

    • Example: Malaria (mosquito-borne)
    • Complex life cycles

Transmission Routes:

Direct Contact:

  • Person-to-person
  • Touching, kissing, sexual contact
  • Example: Cold, flu, herpes

Airborne:

  • Respiratory droplets
  • Coughing, sneezing
  • Example: TB, measles

Food/Water-borne:

  • Contaminated food/water
  • Poor sanitation
  • Example: Cholera, dysentery

Vector-borne:

  • Insects carry disease
  • Mosquitoes, ticks
  • Example: Malaria, Lyme disease

Contaminated Objects:

  • Fomites (surfaces)
  • Example: Norovirus, COVID-19

3. Non-Communicable Diseases (गैर-संचारी रोग)​

Definition:

  • Not caused by infectious pathogens
  • Cannot spread between people
  • Often linked to lifestyle

Risk Factors:

  • Diet: High fat, sugar, salt
  • Physical inactivity: Sedentary lifestyle
  • Smoking: Lung disease, cancer, heart disease
  • Alcohol: Liver disease, cancer
  • Stress: Mental health, high blood pressure
  • Genetics: Inherited predisposition
  • Age: Some diseases increase with age

Examples:

Cardiovascular Disease:

  • Heart disease, stroke
  • Risk factors: High blood pressure, high cholesterol, smoking
  • Lifestyle prevention possible

Cancer (कैंसर):

  • Uncontrolled cell growth
  • Multiple types (lung, breast, skin, colon)
  • Risk factors: Smoking, UV exposure, poor diet

Type 2 Diabetes:

  • High blood glucose
  • Insulin resistance
  • Prevention: Healthy weight, exercise, diet

Respiratory Diseases:

  • Asthma, COPD
  • Risk factors: Smoking, air pollution
  • Manageable with treatment

Immune System (प्रतिरक्षा तंत्र)​

1. Defense Mechanisms​

Non-Specific (Innate) Immunity:

  • First line defense
  • No previous exposure needed
  • Quick response

Barriers:

  • Skin: Physical barrier

    • Prevents entry of pathogens
    • Sweat with antibacterial properties

  • Mucous membranes: Nose, throat, digestive tract

    • Produce mucus (traps pathogens)
    • Stomach acid (kills pathogens)
    • Lysozyme in tears/saliva (enzyme)

  • Cilia: Hair-like structures

    • Move pathogens out
    • Example: Respiratory tract

Internal Defense:

  • Phagocytes: White blood cells that engulf pathogens

    • Neutrophils (most abundant)
    • Macrophages

  • Inflammation: Response to injury/infection

    • Redness, heat, swelling, pain
    • Increased blood flow
    • Brings immune cells to area

  • Complement proteins: Enhance immune response

    • Enhance inflammation
    • Mark pathogens for destruction

2. Specific (Adaptive) Immunity​

T Lymphocytes (T cells):

  • Develop in thymus
  • T helper cells: Coordinate immune response
  • T killer/cytotoxic cells: Destroy infected cells
  • T regulatory cells: Control immune response

B Lymphocytes (B cells):

  • Develop in bone marrow
  • Produce antibodies (immunoglobulins)
  • Memory cells provide lasting immunity

Antibodies (एंटीबॉडी):

  • Proteins produced by B cells
  • Specific to antigen
  • Y-shaped structure
  • Functions:
    • Bind to antigen
    • Mark for destruction (opsonization)
    • Neutralize toxins
    • Prevent pathogen attachment

Antigen-Antibody Reaction:

  • Antigen: Foreign substance (pathogen or part)
  • Antibody: Binds specifically to antigen
  • Specific recognition
  • Forms complex
  • Makes pathogen "visible" to immune system

3. Immune Response Process​

Primary Response (First Exposure):

  1. Pathogen enters body
  2. Antigen recognized
  3. Activation of T and B cells
  4. B cells differentiate:
    • Plasma cells: Produce antibodies
    • Memory cells: Long-term protection
  5. T cells destroy infected cells
  6. Inflammation supports response
  7. Response subsides when pathogen cleared
  8. Memory cells remain

Secondary Response (Re-exposure):

  • Memory cells quickly activated
  • Faster, stronger response
  • Larger antibody production
  • Antibodies of higher affinity
  • Usually prevents disease

4. Vaccination (टीकाकरण)​

Definition:

  • Introduce weakened/dead pathogen
  • Stimulate immune response
  • Without causing disease

Types:

Live Attenuated:

  • Weak/mutated pathogen
  • Good immune response
  • Risk of reversion (rare)
  • Example: Measles

Inactivated (Dead):

  • Killed pathogen
  • Safer, no reversion risk
  • May need boosters
  • Example: Polio, whooping cough

Subunit/Recombinant:

  • Only specific antigen (not whole pathogen)
  • Very safe
  • May need boosters
  • Example: Hepatitis B, HPV

Advantages:

  • Prevents disease
  • Reduces spread
  • Herd immunity (70-95% vaccinated)
  • Cost-effective
  • Public health benefit

Herd Immunity:

  • When enough population vaccinated
  • Disease cannot spread easily
  • Protects vulnerable (allergies, immunocompromised)
  • Percentage varies by disease

Drugs and Effect on Body​

1. Drug Categories​

Medicinal Drugs (औषधीय दवा):

  • Cure or manage disease
  • Prescribed by doctors
  • Regulate transmission across cell membrane or enzyme action
  • Example: Antibiotics, statins, insulin

Recreational Drugs:

  • Psychoactive
  • Affect nervous system
  • Pleasure-seeking
  • Risk of dependence
  • Example: Alcohol, tobacco, cannabis, cocaine

2. Drug Actions​

Mechanism:

  • Bind to receptors (enzyme/protein)
  • Block or enhance function
  • Affect neurotransmitters
  • Alter metabolism

Examples:

  • Antibiotics: Kill bacteria (penicillin, erythromycin)
  • Antivirals: Inhibit virus replication (antiretrovirals for HIV)
  • Statins: Lower cholesterol
  • Insulin: Lowers blood glucose

3. Drug Targets​

Enzyme Inhibition:

  • Block enzyme function
  • Prevent reaction
  • Reduce product (example: statin reduces cholesterol)

Receptor Blocking:

  • Block receptor function
  • Prevent signal transmission
  • Example: Beta-blockers (heart disease)

Membrane Transport:

  • Affect transport across membrane
  • Example: ACE inhibitors (blood pressure)

4. Tolerance and Addiction​

Tolerance:

  • Body adapts to drug
  • Increasing doses needed for same effect
  • Dangerous (overdose risk)
  • Example: Opioids

Addiction:

  • Psychological dependence
  • Physical dependence
  • Withdrawal symptoms
  • Example: Nicotine, alcohol, cocaine

Risks:

  • Health damage
  • Social problems
  • Legal issues
  • Financial costs

Public Health Measures​

1. Disease Prevention​

Control of Communicable Disease:

  • Quarantine: Isolate infected persons
  • Isolation: Separate susceptible from infected
  • Disinfection: Kill pathogens on surfaces
  • Hygiene: Handwashing, sanitation
  • Safe water/food: Prevent transmission

Vaccination Programs:

  • Mass vaccination
  • Childhood schedules
  • Booster doses
  • Herd immunity goal

2. Lifestyle Changes Reduce Risk​

Non-Communicable Disease Prevention:

  • Healthy diet: Vegetables, fruits, whole grains

    • Reduce heart disease, cancer, diabetes

  • Regular exercise: 150 min/week moderate activity

    • Weight management
    • Cardiovascular health
    • Mental health

  • No smoking: Reduce cancer, lung disease

    • Former smokers benefit within years

  • Limit alcohol: Reduce cancer, liver disease

  • Stress management: Mental health, immune function

  • Adequate sleep: Support immunity and metabolism

  • Healthy weight: BMI 18.5-25

3. Health Screening​

Early Detection:

  • Regular check-ups
  • Blood pressure, cholesterol screening
  • Cancer screenings (mammography, colonoscopy)
  • Early treatment more effective

Summary​

Health encompasses:

  • Communicable Diseases: Pathogens transmitted between people
  • Non-Communicable Diseases: Lifestyle-related chronic diseases
  • Immune System: Multi-layered defense
  • Vaccination: Safe prevention of disease
  • Drugs: Treat disease or consequences
  • Public Health: Population-level prevention

Individual and public health measures essential for disease prevention and healthy populations.