SSC CGL - Detailed Guide 2025
Self-Paced Course
Diseases and Immunity
Reference: Lucent GK, NCERT Class 6–12
A disease is a condition that impairs the normal functioning of the body. It may be caused by infections, lifestyle factors, nutritional deficiencies, or genetic disorders.
1. Communicable vs Non-Communicable Diseases
| Type | Communicable Diseases | Non-Communicable Diseases |
|---|---|---|
| Definition | Spread from one person to another | Do not spread from person to person |
| Cause | Pathogens: bacteria, viruses, fungi, protozoa | Genetic, nutritional, environmental, or lifestyle |
| Mode of Transmission | Air, water, food, contact, vectors | Internal malfunction, habits |
| Examples | Tuberculosis, Malaria, AIDS, Flu | Cancer, Diabetes, Hypertension, Asthma |
| Prevention | Isolation, hygiene, vaccination | Healthy lifestyle, early diagnosis, proper treatment |
Carrier: A person who harbors the disease-causing microbe without showing symptoms (e.g. Typhoid Mary).
2. Vaccination and Immunity
Immunity: The body's ability to resist or fight infections and toxins.
| Type of Immunity | Description | Example |
|---|---|---|
| Innate Immunity | Present from birth; non-specific defense | Skin, mucus, WBCs, stomach acid |
| Acquired Immunity | Developed during lifetime; specific to pathogens | Antibodies after infection/vaccine |
Vaccination:
- A process of stimulating the immune system by introducing dead or weakened pathogens (antigens).
- Causes the body to produce antibodies, creating memory cells.
- Prevents future infections by same pathogen.
Common vaccines:
- BCG (for TB)
- MMR (for Measles, Mumps, Rubella)
- OPV (Oral Polio Vaccine)
- Hepatitis B vaccine
Antibodies: Proteins produced by B-cells to neutralize pathogens.
Memory cells: Produced during vaccination or infection; provide long-term protection.
3. Common Diseases
A. Malaria
| Feature | Details |
|---|---|
| Causative Agent | Plasmodium (protozoa) |
| Vector | Female Anopheles mosquito |
| Type of Disease | Protozoan, communicable |
| Affected Organ | Liver (initially), then RBCs |
| Symptoms | Fever (intermittent), chills, vomiting, anemia |
| Diagnosis | Blood smear microscopy |
| Prevention | Mosquito nets, insect repellents, stagnant water control |
| Treatment | Antimalarial drugs (e.g., Chloroquine, Artemisinin) |
Life cycle of Plasmodium involves both mosquito (sexual stage) and human (asexual stage).
B. Tuberculosis (TB)
| Feature | Details |
|---|---|
| Causative Agent | Mycobacterium tuberculosis (bacteria) |
| Mode of Transmission | Airborne droplets from cough or sneeze |
| Affected Organs | Lungs (most common), but can affect bones, brain, kidney |
| Symptoms | Persistent cough (with blood), fever, night sweats, weight loss |
| Diagnosis | Chest X-ray, sputum test, Mantoux test |
| Prevention | BCG vaccine, isolation, good hygiene |
| Treatment | Long-term antibiotics (e.g., isoniazid, rifampicin) |
TB is a notifiable disease — must be reported to public health authorities.
C. AIDS (Acquired ImmunoDeficiency Syndrome)
| Feature | Details |
|---|---|
| Causative Agent | HIV (Human Immunodeficiency Virus) |
| Transmission | Unprotected sex, infected blood transfusion, mother to child |
| Effect on Body | Weakens immune system by destroying helper T-cells |
| Symptoms | Fever, weight loss, fatigue, frequent infections |
| Diagnosis | ELISA, Western blot test |
| Prevention | Safe sex, screening blood, sterile needles |
| Treatment | No permanent cure; ART (antiretroviral therapy) slows progress |
HIV does not spread via casual contact (e.g. hugging, sharing food).
Other Common Communicable Diseases:
- Typhoid (Bacterial; waterborne)
- Dengue (Viral; spread by Aedes mosquito)
- Hepatitis B (Viral; blood/sexual transmission)
- Measles (Viral; airborne)
Other Non-Communicable Diseases:
- Cancer (uncontrolled cell growth)
- Diabetes (insulin deficiency or resistance)
- Hypertension (high blood pressure)
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