We rarely see diseases like smallpox or polio anymore — but diabetes and heart disease are becoming far more common. What does it really mean to be "healthy"?
Key idea
What Does "Health" Really Mean?
According to the WHO, health is a state of complete physical, mental, and social well-being — not merely the absence of disease.
What a healthy person can do
Perform tasks efficiently, cope with difficult situations, and adjust well with peers and society.
Key idea
How Can We Stay Healthy?
1
Healthy habits
A balanced diet, staying active, enough sleep, yoga or pranayama, and avoiding tobacco, alcohol, and addictive drugs.
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A clean environment
Clean air and water matter too — the Air Quality Index (AQI) tells us how clean or polluted the air is. Emotional well-being, like time with friends and family, matters just as much.
Key idea
Symptoms and Signs
1
Symptom
What a person feels — like pain, dizziness, or tiredness.
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2
Sign
What can be seen or measured — like fever, a rash, or high blood pressure.
Key idea
What Is a Disease?
A disease affects the normal working of the body or mindsometimes caused by pathogens, sometimes by poor nutrition or lifestyle.
PathogenA disease-causing organism — bacteria, viruses, fungi, worms, or protozoa.
Key idea
Communicable and Non-communicable Diseases
| Cause | Spreads person to person? | Example
Communicable
A pathogen — Yes — Typhoid, dengue, chickenpox
Non-communicable
Lifestyle, diet, environment — No — Diabetes, asthma, cancer
Key idea
How Diseases Spread
1
Air
Coughing, sneezing — cold, flu, TB.
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2
Contact
Direct or indirect touch.
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3
Food & water
Contamination — typhoid, cholera.
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4
Vectors
Mosquitoes and other carriers — malaria, dengue.
Key idea
Immunity and Vaccines
1
Immunity
The body's natural ability to fight disease, carried out by the immune system.
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Vaccines
Train the immune system to recognise and attack a pathogen — giving acquired immunity. Vaccines are preventive, not curative.
Key idea
Edward Jenner and Smallpox
Jenner discovered that exposure to cowpox protected people against smallpox — leading to the world's first vaccine.
An Indian tradition tooIndia historically used variolation, carried out by teekedaars, against smallpox even before modern vaccines existed.
Key idea
Antibiotics
Antibiotics are medicines that kill bacteria
they work only against bacterial infections, not viruses or protozoa.
A lucky accident
Alexander Fleming discovered penicillin, the first antibiotic, in 1928 — after noticing a mould killing bacteria in a petri dish.
Key idea
Antibiotic Resistance
When medicine stops working. Bacteria that once died from an antibiotic can survive and multiply despite treatment — often from indiscriminate or incomplete use, including in animals. This makes infections harder to treat.
Chapter · Key terms to remember
Key Terms
Health
Complete physical, mental, and social well-being.
Symptom / Sign
What's felt / what's seen or measured.
Pathogen
A disease-causing organism.
Chapter · Key terms to remember
More Key Terms
Communicable disease
Caused by a pathogen, spreads person to person.
Non-communicable disease
Not caused by a pathogen; not contagious.
Immunity
The body's natural ability to fight disease.
Chapter · Key terms to remember
More Key Terms
Vaccine
Trains the immune system to fight a pathogen.
Antibiotic resistance
Bacteria surviving despite antibiotic treatment.
Questions for your notebook
Write these down, then discuss
1
Group these as communicable or non-communicable: Cold and flu, Typhoid, Diabetes, Asthma, Chickenpox.
2
Identify the non-communicable diseases: (i) Typhoid (ii) Asthma (iii) Diabetes (iv) Measles.
3
There's a flu outbreak at school — several classmates are absent, some are coughing and sneezing. (i) What should the school do? (ii) How can you respond kindly to a sick benchmate? (iii) How can you protect yourself and others?
Project as-is — students copy the questions, then the class discusses answers together.