Health, Diseases and Immunity
Health
Health (WHO) is a state of complete physical, mental and social well-being, not just the absence of disease. WHO was founded in 1948; World Health Day is 7 April.
Types of diseases
| Type | Features | Examples |
|---|---|---|
| Infectious (communicable) | Caused by pathogens, spread to others | Cold, TB, malaria |
| Non-infectious | Not spread; lifestyle, genetic, ageing | Cancer, diabetes, hypertension, heart disease |
| Deficiency | Lack of nutrients | Scurvy, rickets, goitre |
| Genetic | Inherited | Haemophilia, thalassemia |
Diseases caused by pathogens
| Pathogen | Disease |
|---|---|
| Virus | Common cold, influenza, polio, measles, mumps, chickenpox, smallpox (eradicated 1980), dengue, rabies, hepatitis A/B/C, AIDS (HIV), COVID-19, Japanese encephalitis, chikungunya |
| Bacteria | Tuberculosis, typhoid, cholera, tetanus, diphtheria, whooping cough, leprosy, plague, anthrax, pneumonia |
| Protozoa | Malaria (Plasmodium), amoebic dysentery, sleeping sickness, kala-azar |
| Fungi | Ringworm, athlete's foot, candidiasis |
| Worms (helminths) | Ascariasis, filariasis (elephantiasis), tapeworm infection |
- Vector: carries the pathogen: female Anopheles mosquito (malaria), Aedes mosquito (dengue, chikungunya, yellow fever), Culex (filaria, Japanese encephalitis), housefly (cholera, typhoid), tsetse fly (sleeping sickness), rat flea (plague), sandfly (kala-azar).
- Mode of spread: air (TB, cold, COVID-19), water and food (cholera, typhoid, jaundice), contact (ringworm, scabies), vector, blood and sexual contact (HIV, hepatitis B).
- Malaria: fever with chills; quinine and chloroquine are medicines. Dengue: low platelets.
- AIDS: caused by HIV, which attacks T-lymphocytes (WBC) and weakens immunity; spreads by blood, unsafe sex and from mother to child; not by touch, mosquito or sharing food. ELISA is a test.
- Tuberculosis: Mycobacterium tuberculosis, discovered by Robert Koch; BCG vaccine; DOTS therapy.
- Cancer: uncontrolled cell division; tumours (benign, malignant); caused by tobacco, radiation, carcinogens. Early detection and surgery, radiotherapy, chemotherapy are treatments.
- Diabetes, hypertension and obesity are lifestyle diseases.
Immunity and vaccines
- Immunity is the body's ability to fight disease. Innate (skin, mucus, acid) and acquired. WBCs produce antibodies against antigens.
- Vaccination: a weak or dead pathogen trains the body to make antibodies: active immunity. Edward Jenner (smallpox, using cowpox, 1796). Passive immunity is from ready-made antibodies (mother's milk, antiserum).
- Important vaccines: BCG (TB), DPT (diphtheria, pertussis, tetanus), OPV and IPV (polio), MMR (measles, mumps, rubella), hepatitis B, HPV and rotavirus. Polio was declared eliminated from India in 2014 (WHO). Pulse Polio is a national programme. Mission Indradhanush raised immunisation.
- Antibiotics work on bacteria, not viruses. Penicillin was found by Fleming (1928). Misusing them causes antibiotic resistance.
- Antiseptics (used on living tissue) and disinfectants (on objects).
- First aid, ORS (oral rehydration solution) for diarrhoea and cholera.
- Allergy: an exaggerated immune response (to pollen, dust, certain foods); antihistamines treat it.
- Drug abuse: alcohol damages the liver (cirrhosis); smoking causes lung cancer and heart disease (nicotine, tar, carbon monoxide); World No Tobacco Day: 31 May; World AIDS Day: 1 December; World TB Day: 24 March; World Malaria Day: 25 April.
Keep practising
Notes are only half the work. Test yourself with questions and discuss doubts with other aspirants.
Prepared for exam revision from the NCERT Science textbooks for Classes 6 to 10 and standard sources. Space missions, awards and records change, so check official sources for recent facts. Found a mistake? Tell us.