Overview
This chapter asks a simple question with a deep answer: what does it really mean to be healthy? You begin with the WHO idea that health is complete physical, mental and social well-being, not just the absence of illness, and see how loneliness or stress can make the body unwell too. You then look at the everyday habits and surroundings that build or damage health: diet, exercise, sleep, screen time, hygiene, clean water, clean air and good relationships. Next you learn how we know we are unwell, separating symptoms that we feel from signs that can be seen or measured, and what a disease and a pathogen are. Diseases fall into two groups. Communicable diseases are caused by bacteria, viruses, protozoa, fungi or worms and spread by air, contact, food and water, insect vectors and animal bites; each route can be blocked by a simple precaution. Non-communicable diseases such as diabetes, cancer and asthma are linked to lifestyle and environment and are now the leading cause of death in India. Finally you study how the body defends itself through immunity, how vaccines give acquired immunity, what antibiotics can and cannot do, and why their misuse breeds resistant bacteria.
हिंदी में पढ़ें
स्वास्थ्य केवल बीमार न होना नहीं है। यह अध्याय शारीरिक, मानसिक और सामाजिक कुशलता, रोगों के फैलने के तरीकों, और टीकों, स्वच्छता तथा दवाओं के समझदारी भरे उपयोग से स्वस्थ रहने के बारे में बताता है।
Learning Objectives
- Explain health as physical, mental and social well-being
- List lifestyle habits and environmental conditions that promote or harm health
- Distinguish between signs and symptoms of disease
- Define disease and pathogen, and classify diseases as communicable or non-communicable
- Describe the routes by which communicable diseases spread and the precautions that block each route
- Explain the causes of non-communicable, chronic and deficiency diseases and how lifestyle changes prevent them
- Explain immunity and how vaccines give acquired immunity
- State what antibiotics can and cannot treat and explain how antibiotic resistance develops
Topics in this chapter
7 topics · tap a topic title to jump straight to it.
What does it mean to be healthy?
1Think first
2The idea, in plain words
Think of a Class 8 student who moves to a new city. He has no friends yet and his parents are busy at work. He spends more and more time on his phone, and slowly he begins to get headaches, loses weight and cannot sleep. No germ has attacked him, yet he is clearly not well. His trouble began with loneliness. A doctor and a school counsellor helped him by cutting down his screen time and helping him make friends.
This story shows that health is much more than “not being sick”. The World Health Organization (WHO) describes health as a state of complete physical, mental and social well-being, and not just the absence of disease. So health has three sides that support one another:
- Physical health: the body works well, grows properly and has energy for work and play.
- Mental health: we can think clearly, handle stress and worry, and feel generally positive.
- Social health: we get along with family, friends and classmates and feel that we belong.
When one side is weak, the others suffer too. Stress and loneliness can cause headaches, poor sleep and loss of appetite, which are physical problems. In the same way, a long illness can make a person sad and cut off from friends. A healthy person usually does daily tasks more efficiently, copes better with difficult situations and adjusts well with others.
India’s traditional system of Ayurveda has a similar idea: good health is a balance between the body, the mind and the surroundings. It recommends a regular daily routine (dinacharya), a routine that changes with the seasons (ritucharya), fresh and wholesome food that suits one’s body type (prakriti), exercise, cleanliness, good sleep and a calm mind. Yoga, meditation and mindfulness help to keep this balance.
Health and happiness are linked in both directions. Being cheerful and active helps us stay healthy, and good health in turn lifts our mood. Keep all three sides in mind whenever you judge whether someone is healthy.
3Worked example
- A student who is physically fit but lonely and anxious is not completely healthy.
- Playing a team game exercises the body and also builds friendships, helping physical and social health together.
- Regular sleep and a daily routine (dinacharya) support both body and mind.
4Your turn
According to the WHO, health is:
5Remember this
Staying healthy: lifestyle and surroundings
1Think first
2The idea, in plain words
Our health depends on two big groups of factors: our lifestyle (how we live every day) and our environment (the surroundings we live in). We control many of these ourselves, which is good news.
Habits that build health
- Eat a balanced diet with plenty of fruits, vegetables and whole grains, and cut down on processed, fatty and sugary food and drinks.
- Stay physically active: play outdoors, walk, run, cycle or exercise.
- Sleep enough, so that the body and mind can rest and repair themselves.
- Keep yourself clean: bathe, wash hands and keep nails trimmed.
- Practise yoga or simple breathing exercises such as pranayama, and take time to relax.
- Say “No” to tobacco, alcohol and addictive drugs.
Habits that harm health include spending too long on phones and screens, eating junk food every day, sleeping late or too little, and skipping meals, especially breakfast.
A clean environment. Imagine two playgrounds: one swept and green, the other full of garbage, stagnant water, flies and mosquitoes. Children who play near the second one fall ill more often, because dirt and still water are breeding places for germs and insects. Keeping our homes, streets and water sources clean protects everyone around us.
Clean air matters as much as clean water. Smoke and dust from vehicles, factories and burning waste can cause coughing and make asthma worse. The Air Quality Index (AQI) is a number that tells us how clean or polluted the air is on a given day, so that we can take care, for example by staying indoors when the air is very poor.
Finally, remember the social side. Even with good food and clean air, a person who is lonely or upset will not feel well. Talking, laughing and spending time with family and friends keep the mind healthy.
3Worked example
- Replacing a daily packet of chips with a fruit reduces fat, salt and processed food in the diet.
- Covering water containers and draining stagnant water near the house removes places where mosquitoes breed.
- Checking the AQI before an outdoor run on a smoggy winter morning.
4Your turn
Which of these is a habit that HARMS health?
5Remember this
Signs, symptoms and types of disease
1Think first
2The idea, in plain words
Our body normally works in a steady, balanced way. When something inside stops working properly, we feel unwell. A disease is a condition that disturbs the normal working of the body or the mind. It may happen when one or more organs or organ systems do not function properly.
Symptoms and signs. A symptom is what the patient feels, such as pain, tiredness or dizziness. Only the patient can tell us about it. A sign is something that another person can see or measure, such as a rash, swelling, a high body temperature on a thermometer, or high blood pressure. Doctors use both to work out what is wrong. For example, “I feel feverish and tired” are symptoms, while “the thermometer reads 102 °F” is a sign.
Causes of disease. Some diseases are caused by tiny living things such as bacteria, viruses, fungi, protozoa (single-celled organisms) and worms. Organisms that cause disease are called pathogens. Other diseases come from poor nutrition or an unhealthy lifestyle. Some diseases last only a few days; others last for a long time and need regular care.
Diseases are grouped into two main types, based on their cause and whether they spread:
| Communicable | Non-communicable |
| Caused by pathogens | Not caused by pathogens |
| Can spread from one person to another | Do not spread from person to person |
| Examples: typhoid, dengue, flu, chickenpox, COVID-19 | Examples: cancer, diabetes, asthma |
| Prevented mainly by hygiene, clean water, vector control and vaccines | Linked to lifestyle, diet and/or environment; prevented mainly by healthy habits |
In the past, communicable diseases such as smallpox and polio were the biggest worry. Today, in India, non-communicable diseases such as diabetes, heart disease and cancer have become more common and cause most deaths. The reasons include eating more processed food, exercising less and people living longer. Knowing which type a disease belongs to tells us how to prevent it.
3Worked example
- Pain and dizziness are symptoms; a rash and a thermometer reading of high temperature are signs.
- Typhoid is communicable because it is caused by bacteria that can pass to others.
- Asthma is non-communicable; you cannot catch it from a friend.
4Your turn
Which of the following is a SIGN rather than a symptom?
5Remember this
How communicable diseases spread and how to stop them
1Think first
2The idea, in plain words
Every communicable disease is caused by a pathogen, and the pathogen has to travel from an infected person to a healthy one. Knowing the route tells us how to block it. The main routes are:
- Through air: when an infected person coughs, sneezes or even talks, tiny droplets carrying germs float in the air. Colds, flu, chickenpox, measles and tuberculosis spread this way.
- Direct contact: touching, hugging or shaking hands with an infected person.
- Indirect contact: sharing towels, handkerchiefs, utensils or other personal items.
- Contaminated food and water: cholera, typhoid, hepatitis A and roundworm infection (ascariasis) spread when food or water is polluted, often by human waste.
- Vectors: insects such as mosquitoes and houseflies that carry pathogens. Mosquitoes spread malaria (caused by a protozoan) and dengue (caused by a virus).
- Animal bites: a bite from a rabid animal can pass on rabies.
Roundworms and other worms that live in our intestines are parasites: they live in or on another living being and feed on its nutrients. They can cause poor growth, weight loss and anaemia.
Breaking the chain. Each precaution blocks one route:
| Route | How to block it |
| Air | Cover mouth and nose when coughing or sneezing; wear a mask in crowds |
| Contact | Wash hands with soap and water; do not share towels or handkerchiefs |
| Food and water | Drink boiled or purified water; eat properly cooked food; use toilets |
| Mosquitoes | Use nets and repellents; wear long sleeves; drain stagnant water |
Staying at home and resting when you are unwell helps you recover and stops the disease reaching others. Vaccines, discussed later, protect against many of these diseases too.
Dengue cases usually rise in and after the monsoon, when rainwater collects in pots, tyres and coolers and mosquitoes breed. That is why clearing still water before the rains is such an effective step.
3Worked example
- Covering a sneeze with the elbow stops droplets reaching people nearby.
- Boiling drinking water kills the bacteria that cause cholera and typhoid.
- Emptying water from old tyres and coolers cuts down the mosquitoes that carry dengue.
4Your turn
Which disease is spread by a vector?
5Remember this
Non-communicable diseases and lifestyle
1Think first
2The idea, in plain words
Non-communicable diseases (NCDs) are not caused by pathogens and do not spread from person to person. They are linked to lifestyle, diet and the environment. Today they are the most common cause of death in India.
Chronic diseases. Diseases such as cancer, diabetes and asthma often last a long time, more than three months, and are called chronic diseases. They usually cannot be cured quickly, but they can be controlled.
Deficiency diseases are also non-communicable. They are caused by a lack of a particular nutrient in the diet: scurvy (lack of vitamin C), anaemia (lack of iron) and goitre (lack of iodine). Too much of some vitamins or minerals can also harm the body, so a balanced diet is the safe path.
Diabetes is a good example of a lifestyle-linked disease. India now has one of the largest numbers of people with diabetes in the world, and it is appearing even in children. It usually develops from a mix of reasons: hormonal imbalance, unhealthy eating, lack of physical activity and being overweight or obese. Common warning signs and symptoms are:
- frequent urination and excessive thirst,
- weight loss and tiredness,
- wounds that heal slowly.
Obesity and high blood pressure are other common lifestyle-related problems. Obesity can be reduced by eating a balanced diet and exercising regularly, and high blood pressure is helped by eating less salt, staying active, managing stress and avoiding tobacco and alcohol.
Tobacco, unhealthy diet and pollution also raise the risk of cancer. The Indian researcher Kamal Ranadive (1917–2001) studied how hormones and certain viruses are linked with cancer, and her work highlighted how tobacco, diet and pollution add to the risk.
The key message is that most NCDs can be prevented or delayed by the habits learnt earlier: balanced meals with less oil and sugar, daily activity, enough sleep, less screen time and staying away from tobacco and alcohol. Regular health check-ups catch problems such as high blood sugar or blood pressure early.
3Worked example
- Scurvy, caused by too little vitamin C, is a deficiency disease.
- Excessive thirst and frequent urination can be early signs of diabetes.
- Eating less salt and walking daily help to control high blood pressure.
4Your turn
Which of these is a chronic, non-communicable disease?
5Remember this
Immunity and vaccines
1Think first
2The idea, in plain words
Two friends live in the same house and eat the same food, yet one catches every cold and the other rarely does. The difference lies in immunity, the natural ability of the body to fight disease. The body has a special immune system that recognises and destroys harmful germs.
Why the second attack is weaker. When the body meets a pathogen for the first time, the immune system takes time to recognise it, so the response is slow and small, and we may fall ill. The immune system remembers the germ. When the same pathogen enters again, the response is quick and much stronger, and the germ is usually destroyed before we feel sick.
Vaccines use this memory. A vaccine trains the immune system to recognise a particular germ without causing the disease. The protection a person develops after exposure to a pathogen or a vaccine is called acquired immunity. Vaccines can be made from:
- weakened or dead pathogens,
- inactive or harmless parts of a pathogen,
- instructions that make our own cells produce a harmless part of the germ, which the immune system then learns to fight (in some newer vaccines).
For example, the tetanus injection given after a deep cut contains an inactivated form of the poison made by tetanus bacteria. The body learns to defend against it without getting the disease. The drops and injections you got as a baby protect you against diseases such as polio, measles, tetanus and hepatitis.
The first vaccine. In the late 1700s the English doctor Edward Jenner noticed that milkmaids who had caught cowpox, a mild disease, did not get the deadly smallpox. He guessed that material from cowpox blisters gave protection, tested it on a boy, and found that the boy did not fall ill when exposed to smallpox. Mass vaccination later wiped out smallpox from the whole world by the end of the 1970s. Even earlier, India had a practice called variolation, in which material from a smallpox sore was scratched into the skin to cause a mild infection; those who did it were called teekedaars.
Vaccines prevent disease; they do not cure a person who is already sick. They protect not only you but also the people around you. India is one of the world’s largest makers of vaccines, and the scientist Maharaj Kishan Bhan played a key role in developing the rotavirus vaccine that protects children from diarrhoea.
3Worked example
- A child who had chickenpox once rarely gets it again, because the immune system remembers it.
- The tetanus shot after an injury uses an inactivated toxin to build protection.
- Smallpox was eradicated worldwide through mass vaccination.
4Your turn
Which statement about vaccines is correct?
5Remember this
Treatment: antibiotics, resistance and long-term care
1Think first
2The idea, in plain words
If the immune system cannot stop an infection, we fall ill and need a doctor. For infections caused by bacteria, the doctor may prescribe antibiotics, medicines that kill bacteria or stop them from growing. Antibiotics act on parts of bacterial cells that are different from our own cells. That is why they do not work against viruses (colds, flu) or against protozoa (malaria).
A lucky discovery. In 1928 Alexander Fleming, a bacteriologist in London, noticed that a mould growing on one of his old culture dishes had stopped the bacteria around it from growing. The mould released a substance that killed bacteria. This became penicillin, the first antibiotic, which has since saved millions of lives.
Antibiotic resistance. When antibiotics are taken without need, or the course is stopped early, a few bacteria that happen to survive the medicine are left behind. The antibiotic kills the sensitive bacteria (and also helpful bacteria in the body), so the resistant ones multiply and take over. They can even pass resistance to other bacteria. The result is that an antibiotic which once worked now fails. Resistant bacteria spread through people, hospitals, and also through animals treated with antibiotics, their manure, soil and crops. Common infections then become harder to treat and can lead to longer illness and even death.
Using antibiotics wisely:
- take them only when a doctor prescribes them,
- take the full dose for the full number of days,
- never take antibiotics for a cold, cough or flu caused by a virus,
- do not give antibiotics to farm animals without a vet’s advice.
Traditional systems such as Ayurveda, Siddha and Unani use herbs, oils and minerals and stress a healthy lifestyle and diet. They help with some conditions and everyday well-being, but they may not work for every disease or at every stage.
Care for non-communicable diseases aims to manage symptoms and improve quality of life through medicines, lifestyle changes and rehabilitation. Early diagnosis and continuous care slow the disease and prevent complications. And above all, remember: prevention is better than cure. A community campaign in Bhadrak district, Odisha, that helped people build and use toilets led to fewer cases of diarrhoea among children.
3Worked example
- A doctor prescribes an antibiotic for typhoid, which is caused by bacteria.
- An antibiotic will not help a common cold, because a cold is caused by a virus.
- Stopping a 5-day antibiotic course on day 2 can leave resistant bacteria alive.
4Your turn
Antibiotic resistance means that:
5Remember this
Key Concepts
- Health
- A state of complete physical, mental and social well-being, not merely the absence of disease (WHO).
- Lifestyle
- The way we live every day: diet, activity, sleep, habits and use of screens.
- Air Quality Index (AQI)
- A number that tells how clean or polluted the air is on a given day.
- Symptom
- What a patient feels, such as pain, tiredness or dizziness.
- Sign
- Something that can be seen or measured, such as a rash, swelling or high temperature.
- Disease
- A condition that disturbs the normal working of the body or the mind.
- Pathogen
- A disease-causing organism such as a bacterium, virus, fungus, protozoan or worm.
- Communicable disease
- A disease caused by a pathogen that can spread from one person to another, e.g. typhoid, dengue, flu.
- Non-communicable disease
- A disease not caused by a pathogen and not spread between people, e.g. diabetes, cancer, asthma.
- Vector
- An insect, such as a mosquito or housefly, that carries pathogens from one host to another.
- Parasite
- An organism that lives in or on another living being and feeds on it, e.g. roundworm.
- Chronic disease
- A disease that lasts a long time, more than three months, such as diabetes or asthma.
- Deficiency disease
- A disease caused by lack of a nutrient in the diet, e.g. scurvy, anaemia, goitre.
- Immunity
- The natural ability of the body to fight disease.
- Immune system
- The body system that recognises and destroys harmful germs.
- Acquired immunity
- Protection the body develops after exposure to a pathogen or a vaccine.
- Vaccine
- A preparation of weakened, dead or harmless parts of a pathogen that trains the immune system to prevent a disease.
- Antibiotic
- A medicine that kills or stops the growth of bacteria; it does not work on viruses.
- Antibiotic resistance
- The ability of bacteria to survive and multiply despite an antibiotic that used to kill them.
End-of-Chapter Trial Paper & Test Questions
Topic-wise questions to test your understanding of every concept in this chapter.
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How does the WHO define health? Name its three aspects. / विश्व स्वास्थ्य संगठन (WHO) स्वास्थ्य की परिभाषा कैसे देता है? इसके तीन पहलुओं के नाम लिखिए।
Show answer
The WHO defines health as a state of complete physical, mental and social well-being, and not merely the absence of disease. Its three aspects are physical, mental and social health. / WHO के अनुसार स्वास्थ्य पूर्ण शारीरिक, मानसिक और सामाजिक कुशलता की अवस्था है, केवल रोग का न होना नहीं। इसके तीन पहलू शारीरिक, मानसिक और सामाजिक स्वास्थ्य हैं।
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What is the difference between a sign and a symptom? Give one example of each. / चिह्न (साइन) और लक्षण में क्या अंतर है? प्रत्येक का एक उदाहरण दीजिए।
Show answer
A symptom is what the patient feels, such as pain or tiredness. A sign is something that can be seen or measured, such as a rash or a high temperature on a thermometer. / लक्षण वह है जो रोगी स्वयं महसूस करता है, जैसे दर्द या थकान। चिह्न वह है जिसे देखा या मापा जा सकता है, जैसे चकत्ते या थर्मामीटर पर तेज़ बुखार।
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Identify the non-communicable diseases: typhoid, asthma, diabetes, measles. / असंचारी रोग पहचानिए: टाइफ़ाइड, दमा, मधुमेह, खसरा।
Show answer
Asthma and diabetes are non-communicable diseases, because they are not caused by pathogens and do not spread from person to person. Typhoid and measles are communicable. / दमा और मधुमेह असंचारी रोग हैं, क्योंकि ये रोगाणुओं से नहीं होते और एक व्यक्ति से दूसरे में नहीं फैलते। टाइफ़ाइड और खसरा संचारी रोग हैं।
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Which diseases may spread if drinking water is contaminated by the excreta of an infected person: hepatitis A, tuberculosis, polio, cholera, chickenpox? / यदि पीने का पानी संक्रमित व्यक्ति के मल से दूषित हो जाए तो कौन-से रोग फैल सकते हैं: हेपेटाइटिस A, क्षयरोग, पोलियो, हैजा, चेचक (छोटी माता)?
Show answer
Hepatitis A, polio and cholera can spread through water contaminated with excreta. Tuberculosis and chickenpox spread mainly through the air. / हेपेटाइटिस A, पोलियो और हैजा मल से दूषित पानी से फैल सकते हैं। क्षयरोग और छोटी माता मुख्य रूप से हवा से फैलते हैं।
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What are vectors? Name two diseases spread by mosquitoes and two ways to prevent them. / रोगवाहक क्या हैं? मच्छरों से फैलने वाले दो रोगों और उनसे बचाव के दो उपायों के नाम लिखिए।
Show answer
Vectors are insects such as mosquitoes and houseflies that carry pathogens from one person to another. Mosquitoes spread malaria and dengue. They can be prevented by using mosquito nets and repellents and by removing stagnant water where mosquitoes breed. / रोगवाहक वे कीट हैं, जैसे मच्छर और मक्खी, जो रोगाणुओं को एक व्यक्ति से दूसरे तक पहुँचाते हैं। मच्छर मलेरिया और डेंगू फैलाते हैं। मच्छरदानी और मच्छर-रोधी क्रीम का प्रयोग करके तथा रुके हुए पानी को हटाकर इनसे बचा जा सकता है।
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Why are non-communicable diseases like diabetes becoming more common in India? / भारत में मधुमेह जैसे असंचारी रोग अधिक आम क्यों होते जा रहे हैं?
Show answer
They are becoming more common because of changes in lifestyle: people eat more processed, oily and sugary food, exercise less, spend more time on screens, and live longer. Obesity and hormonal imbalance also add to the risk of diabetes. / जीवनशैली में बदलाव के कारण ये रोग बढ़ रहे हैं: लोग अधिक प्रसंस्कृत, तला हुआ और मीठा भोजन खाते हैं, कम व्यायाम करते हैं, स्क्रीन पर अधिक समय बिताते हैं और अधिक लंबा जीते हैं। मोटापा और हॉर्मोन का असंतुलन भी मधुमेह का जोखिम बढ़ाते हैं।
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How does a vaccine protect us? Is it preventive or curative? / टीका हमारी रक्षा कैसे करता है? क्या यह रोग से बचाता है या रोग का इलाज करता है?
Show answer
A vaccine contains weakened or dead pathogens, or harmless parts of them, which train the immune system to recognise the germ. If the real germ enters later, the body fights it quickly. A vaccine is preventive, not curative. / टीके में कमज़ोर या मृत रोगाणु, या उनके हानिरहित भाग होते हैं, जो प्रतिरक्षा तंत्र को रोगाणु पहचानना सिखाते हैं। बाद में असली रोगाणु आने पर शरीर उससे जल्दी लड़ता है। टीका रोग से बचाता है, इलाज नहीं करता।
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Why is the immune response stronger when the body meets the same pathogen a second time? / एक ही रोगाणु से दूसरी बार सामना होने पर शरीर की प्रतिरक्षा प्रतिक्रिया अधिक तीव्र क्यों होती है?
Show answer
During the first exposure the immune system learns to recognise the pathogen and remembers it. On the second exposure it recognises the germ at once, so it responds faster and much more strongly. / पहली बार सामना होने पर प्रतिरक्षा तंत्र रोगाणु को पहचानना सीखता है और उसे याद रखता है। दूसरी बार वह उसे तुरंत पहचान लेता है, इसलिए प्रतिक्रिया अधिक तेज़ और प्रबल होती है।
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Why should we not take an antibiotic for a cold, cough or flu? / सर्दी, खाँसी या फ़्लू में एंटीबायोटिक क्यों नहीं लेना चाहिए?
Show answer
Colds and flu are caused by viruses, and antibiotics act only on bacteria, so they do not help. Taking them without need also helps bacteria become resistant to antibiotics. / सर्दी और फ़्लू विषाणुओं से होते हैं और एंटीबायोटिक केवल जीवाणुओं पर काम करते हैं, इसलिए इनसे लाभ नहीं होता। बिना आवश्यकता इन्हें लेने से जीवाणु एंटीबायोटिक के प्रति प्रतिरोधी भी बन जाते हैं।
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What is antibiotic resistance and how can we reduce it? / एंटीबायोटिक प्रतिरोध क्या है और इसे कैसे कम किया जा सकता है?
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Antibiotic resistance is when bacteria that were once killed by an antibiotic survive and multiply despite it. We can reduce it by taking antibiotics only on a doctor’s prescription, completing the full course, and not using them for viral infections or in farm animals without need. / जब वे जीवाणु, जो पहले किसी एंटीबायोटिक से मर जाते थे, उसके बावजूद जीवित रहकर बढ़ने लगें, तो उसे एंटीबायोटिक प्रतिरोध कहते हैं। एंटीबायोटिक केवल डॉक्टर की पर्ची पर लेकर, पूरा कोर्स करके, और विषाणु संक्रमण में या पशुओं में बिना आवश्यकता प्रयोग न करके इसे कम किया जा सकता है।
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