The Ultimate Treasure

1. Is health more than "not being sick"? (3.1)

Most people think a healthy person is simply someone who is not ill. The chapter pushes back on this. According to the World Health Organization (WHO):

So health has three aspects (Fig. 3.1) that must all be in balance:

• Physical — the body works well; you can run, study and do daily tasks with energy.
• Mental — you feel positive, can handle stress, sleep well and concentrate.
• Social — you have good relationships and get along with family, friends and society.

The opening story (Activity 3.1) makes this concrete: a Grade 8 boy moves to a new city, has no friends, busy parents, and spends hours on his phone. He becomes lonely, gets headaches, loses weight and cannot sleep. A doctor advised less screen time and a counsellor helped him make friends. He had no "germ" disease at all — his habits and surroundings damaged his mental and social well-being, which then harmed his body. Health and happiness are closely related.

Our scientific heritage: Ayurveda teaches that true health is a balance of body, mind and surroundings. Following dinacharya (daily routine) and ritucharya (seasonal routine), eating fresh food suited to one's prakriti (body constitution), plus exercise, cleanliness, restful sleep and a calm mind — supported by yoga and meditation — keep us well.

2. How can we stay healthy? (3.2)

Our health depends on two things we can shape: our lifestyle (how we live) and our environment (our surroundings).

3.2.1 A healthy lifestyle — the chapter's checklist (Fig. 3.2):

• Eat a balanced diet with plenty of fruits, vegetables and whole grains.
• Avoid processed, fatty or sugary food and drinks (junk food).
• Stay physically active — play outdoors, walk, run, cycle, exercise.
• Limit screen time and spend more time in nature; get enough sleep to rest and recover.
• Practise yoga or breathing exercises like pranayama to manage stress.
• Say "NO" to harmful substances — tobacco, alcohol and addictive drugs.

3.2.2 Keep the environment clean — a clean, well-maintained area has fewer flies and mosquitoes, so people there fall sick less often than those in dirty, polluted areas. Clean air and water are essential. In cities, air pollution from vehicles and factories causes coughing and asthma; the Air Quality Index (AQI) tells us how clean the air is. And remember — even with good food and a clean home, we feel low when lonely or upset, so spending time with friends and family keeps the mind healthy too.

3. How do we know we are unwell? (3.3)

The body normally works in a steady way. Feeling unwell means something inside is not working as it should. Doctors look at two clues:

• Symptom — what the patient feels, which cannot be directly seen by others: pain, tiredness, dizziness, nausea.
• Sign — something that can be seen or measured: fever (high body temperature), a rash, high blood pressure, swelling.

Easy way to remember: a Symptom is Self-felt; a sign can be shown/measured by a thermometer or test. Together they help doctors figure out the disease.

4. Diseases — causes and the two main types (3.4)

A disease is a condition that affects the normal working of the body or mind, usually when one or more organs or organ systems stop working properly. Some diseases come from germs — bacteria, viruses, fungi, worms or protozoa (single-celled organisms). These disease-causing organisms are called pathogens. Other diseases come from poor nutrition or an unhealthy lifestyle. Diseases split into two big groups:

• Communicable diseases — caused by pathogens; they spread from one person to another. Examples: typhoid, dengue, flu, chickenpox, COVID-19.
• Non-communicable diseases (NCDs) — not caused by pathogens and do not spread. Examples: cancer, diabetes, heart disease, asthma. They are linked to lifestyle, diet and/or environment.

A key modern fact: in earlier times communicable diseases like smallpox and polio were the big killers. Today, because people eat more processed food, exercise less and live longer, NCDs are now the most common cause of death in India. That is the answer to the chapter's "Probe and ponder" question about why diabetes and heart problems are rising while smallpox/polio are rare.

5. How communicable diseases spread (3.4.1)

All communicable diseases are caused by pathogens that enter the body through the air we breathe or through contaminated food and water. The main routes of spread (Fig. 3.4) are:

• Through air — an infected person coughs or sneezes (e.g. common cold, flu, TB).
• Direct contact — touching, shaking hands.
• Indirect contact — sharing personal items like towels and handkerchiefs.
• Through contaminated water and food — e.g. cholera, typhoid.
• Through vectors — insects like mosquitoes and houseflies that carry pathogens are called vectors (e.g. malaria, dengue).
• Through rabid animals — a bite from an infected animal.

Some communicable diseases are caused by worms that live inside the digestive system, feed on our nutrients and live as parasites (organisms that live in or on another living being). These spread through contaminated food, water, soil or contact.

6. Table 3.1 — common communicable diseases (must-memorise)

This table is the single highest-yield part of the chapter. Learn the causal agent and spread route for each.

(a) Spread through the air:

• Common cold & influenza (flu) — Virus; respiratory tract. Symptoms: nasal congestion, sore throat, fever, cough, body ache.
• Chickenpox — Virus; respiratory tract & skin. Mild fever, itchy rashes, blisters. Prevention includes isolation and vaccination.
• Measles — Virus; skin & respiratory tract. Fever, sore throat, reddish rashes on neck, ears, skin.
• Tuberculosis (TB) — Bacteria; lungs. Cough, fever, fatigue, loss of appetite, night sweats.

(b) Spread through contaminated water and food:

• Hepatitis A — Virus; liver. Fatigue, fever, nausea, vomiting, jaundice.
• Cholera — Bacteria; intestine. Diarrhoea and dehydration.
• Typhoid — Bacteria; intestine. Headache, abdominal discomfort, fever, diarrhoea.
• Ascariasis (roundworms) — Worms; intestine. Worms in stool, poor growth, weight loss, anaemia.

(c) Transmitted by insects (vectors):

• Malaria — Protozoa; affects skin/blood. High fever, profuse sweating, periodic chills.
• Dengue fever ("break-bone fever") — Virus; skin/blood. Fever, headache, muscle and joint pain, nausea.

Watch out: malaria is the odd one out — it is caused by a protozoan, not a virus or bacterium. Dengue is a virus. Both spread by mosquito, prevented by nets, repellents, long-sleeved clothes and removing still water where mosquitoes breed.

7. Simple precautions against communicable diseases

From Table 3.1 the chapter lists easy but powerful precautions:

• Keep ourselves and our surroundings clean; practise basic hygiene daily.
• Wash hands with soap and water to remove pathogens (regular handwashing cuts infection by ~50%).
• Cover the mouth and nose while coughing or sneezing; wear a mask in crowded places.
• Avoid sharing personal items like towels and handkerchiefs.
• Keep home, food and water clean; drink boiled water and eat properly cooked food.
• Stay home and rest when unwell — this helps recovery and stops you spreading the disease.

8. Non-communicable diseases (3.4.2)

NCDs like cancer, diabetes and asthma are not spread by germs — they are linked to lifestyle, diet and environment, and are the most common cause of death in India.

• Deficiency diseases — caused by a lack of specific nutrients (minerals/vitamins) in the diet. From Grade 6 you know: scurvy (lack of vitamin C), anaemia (lack of iron) and goitre (lack of iodine). These are also non-communicable.
• Chronic diseases — diseases that persist a long time (more than 3 months), such as cancer, diabetes and asthma.
• Diabetes — becoming common in adults and children; India has one of the highest numbers in the world. It develops from hormonal imbalance, unhealthy eating, lack of physical activity and being overweight/obese. Signs: frequent urination, excessive thirst, weight loss, tiredness, slow healing.
• NCDs can often be prevented or managed with a balanced diet, regular exercise and healthy habits — "prevention is better than cure."

Be a scientist: Kamal Ranadive (1917–2001), a pioneering Indian biomedical researcher, studied how hormones and certain viruses are linked to cancer, and showed how tobacco, diet and pollution raise cancer risk — underlining the value of a healthy lifestyle.

9. Immunity and vaccines (3.5)

You may notice some people fall sick more often than others in the same place. The reason is immunity — the body's natural ability to fight diseases, run by a special immune system.

The drops and injections you took as a child (for polio, measles, tetanus, hepatitis) are vaccines. A vaccine trains the immune system to recognise and attack a particular germ, giving acquired immunity — protection developed after exposure to a pathogen or vaccine. Vaccines are made from:

• Weakened or dead pathogens (viruses or bacteria),
• Inactive or harmless parts of the pathogen (e.g. a tetanus shot uses an inactivated bacterial toxin), or
• Newer vaccines that instruct our own body cells to make a harmless part of the germ, which the immune system then learns to fight.

Why a second exposure is fought better (exercise Q11): the first time the body meets a pathogen, the immune response is slow and weak. The immune system "remembers" that germ, so on the next exposure it responds much faster and stronger. This memory is exactly what a vaccine creates without making us ill.

10. Edward Jenner and the smallpox vaccine

Smallpox was a deadly disease that caused blisters and killed millions. A milder disease seen in cows, called cowpox, could also infect humans. In the late 1700s, the English doctor Edward Jenner observed that milkmaids who had cowpox did not catch smallpox. He hypothesised that something in cowpox blisters protected them, tested it by injecting cowpox material into a boy, and found the boy resisted smallpox. This was the first vaccine; mass vaccination later eradicated smallpox worldwide (declared eradicated in 1979).

Our scientific heritage: long before modern vaccines, India used variolation — taking material from a smallpox sore to scratch the skin and create a mild infection that built immunity. The people who did this were called teekedaars.

Ever heard of...: India is one of the world's largest vaccine producers, supplying vaccines to many countries and playing a key role during COVID-19. Maharaj Kishan Bhan helped develop the affordable Rotavirus vaccine, which protects children from diarrhoea.

11. Treatment, antibiotics and antibiotic resistance (3.5.1)

If the immune system fails and we fall ill, a doctor may give antibiotics — medicines that kill bacteria. They work by targeting parts of bacterial cells that are different from human cells.

Antibiotic resistance: the indiscriminate or wrong use of antibiotics (taking them when not needed, or not finishing the full dose) has made them less effective. Antibiotic resistance is when bacteria that were once killed by an antibiotic now survive and multiply despite the treatment. This makes common infections harder to treat and raises the risk of complications and death.

How resistance develops: a few bacteria already resist the antibiotic; when the antibiotic kills the others (including helpful bacteria), the resistant ones survive, multiply and take over, and can even pass resistance to other bacteria. To prevent it: use antibiotics only when prescribed by a doctor, in the correct dose, for the full duration, and avoid giving them needlessly (e.g. to cattle).

Penicillin — the first antibiotic — was discovered by chance in 1928 by Alexander Fleming, who noticed a mould stopping bacteria from growing in a petri dish.

For NCDs, treatment focuses on managing symptoms through medication, lifestyle changes and rehabilitation; early diagnosis and continuous care control the disease and prevent complications. Traditional systems (Ayurveda, Siddha, Unani) use herbs and minerals and a healthy lifestyle, useful for everyday well-being but not effective for all diseases at all stages.

12. Worked applications (from the chapter's exercises)

13. Common mistakes to avoid

• Defining health as "absence of disease" — WHO needs physical + mental + social well-being.
• Mixing up symptom (felt) and sign (seen/measured).
• Calling malaria a viral disease — it is caused by a protozoan; dengue is the viral mosquito disease.
• Thinking antibiotics cure colds/flu — those are viral; antibiotics only kill bacteria.
• Saying vaccines cure disease — they are preventive, given before infection.
• Listing diabetes/asthma/cancer as communicable — they are non-communicable (lifestyle-linked).

14. Quick revision checklist

• Health = complete physical + mental + social well-being (WHO).
• Symptom = self-felt; Sign = seen/measured.
• Communicable = pathogens, spreads; Non-communicable = lifestyle/diet, no spread.
• Pathogens: bacteria, viruses, fungi, protozoa, worms. Vectors = disease-carrying insects.
• Deficiency diseases: scurvy (vit C), anaemia (iron), goitre (iodine).
• Immunity = natural defence; vaccine = trains it, preventive not curative.
• Antibiotics kill bacteria only; misuse → antibiotic resistance.