1
The closest meaning of health is —
💡 Hint:
Being well.
Explanation:
Health is functioning properly.
Class 9 · Science · Chapter 13 · बिहार बोर्ड (BSEB)CBSE · NCERT 2026-27
Why Do We Fall Ill
Why Do We Fall Ill
How to use this page:
1. Read — 13.1 disaster · 13.2 water · 13.3 waste · 13.4 survey · 13.5 antibiotics · 13.6 height · 13.7 rabies, diagram, worked example, board tip
2. Check — each lesson has its own questions; the number follows the lesson
3. Mastery ★ — all of that lesson correct. Redo the wrong ones
4. The picture to remember is a chain, in which disease goes from a sick person through air, water or a vector to the next person.
In the Bihar book this is chapter 13, and the Exploration book does not place this topic at the same number. Progress stays in this browser.
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- 1 Health and its failure — Activities 13.1, 13.2, 13.3
- 2 Acute and chronic — Activity 13.4
- 3 Infectious agents — Activity 13.5
- 4 The paths of spread
- 5 Prevention and treatment — Activity 13.6
- 6 Immunisation — Activity 13.7
- Chapter winner — every lesson at mastery ★
🎬 Shorts
This chapter has no Short on the channel yet, so ten empty cards are not shown. The notes, diagrams and checks are complete.
📄 PDF download — notes + answer key
Health and its failure — Activities 13.1, 13.2, 13.3
स्वास्थ्य और उसका गिरना — क्रियाकलाप 13.1, 13.2, 13.3 · Section 13.1 · Activities 13.1 to 13.3
Being well, not only the absence of diseaseNotes
Health means being able to function properly. A grandmother going to the market, a child playing and a steady mind all belong here. The body, the mind and the society around are joined.
Disease means that some part of the body or the mind has stopped its own work. A person free of disease can still be unwell from dirty water and hunger. So the conditions for good health and the conditions for freedom from disease are not exactly the same.
Activities 13.1, 13.2 and 13.3Activity
In 13.1 take a disaster such as an earthquake or a cyclone. Some injuries happen while the event is on. Some illnesses come later, because water, houses and food break down. Both groups are caused by the disaster, and the time is different.
In 13.2 ask how the panchayat or the municipal corporation supplies clean drinking water and whether it reaches every home. In 13.3 ask who lifts the solid waste of the neighbourhood. If the measures are few, also write how a family can cut one day of waste.
Worked exampleExample
Question: A person has no named disease, yet is weak. Should that person be called healthy?
Answer: No. Having no disease is only one part of health. Food, clean water and the capacity to function also have to be seen.
10-second revision
- Health = functioning properly
- Disease and being unwell are not exactly the same
- Clean water and waste are public health
Board tip · BSEBBoard tip
In an answer about two conditions, write both personal and public ones.
Board tip · CBSEBoard tip
Do not cut a later illness off from the disaster. The cause still remains afterwards.
Check your understandingall correct = mastery ★
2
Having no disease is by itself complete health.
Explanation:
False — food, water and society also count in health.
3
Ask the ______ or the municipal corporation about clean drinking water.
💡 Hint:
Activity 13.2.
Explanation:
The panchayat.
4
An illness that spreads weeks after an earthquake —
💡 Hint:
The second group in Activity 13.1.
Explanation:
Broken water and houses can cause a later illness.
5
Write two conditions for good health.
Model answer (board format)
Clean drinking water and enough food. Clearing waste, or the support of society, is also a correct condition.
Check your answer:
Acute and chronic — Activity 13.4
तीव्र और दीर्घकालिक — क्रियाकलाप 13.4 · Sections 13.2.2–13.2.3 · Activity 13.4
Duration changes how we see a diseaseNotes
Some diseases last a very short time. These are called acute. A common cold is acute. Some diseases run for a long time. These are called chronic. Elephantiasis is chronic.
A long disease pulls down weight, study and earnings. A short disease often heals and does not stay behind. So a chronic disease weighs more on a poor family. Causes also have two levels. The immediate cause can be a microbe. A contributory cause can be dirty water or weak food.
Activity 13.4 — the count in the neighbourhoodActivity
Ask: how many people had an acute disease in the last three months, how many developed a chronic disease in the same period, and how many people in the neighbourhood are living with a chronic disease in all.
The first and the second counts can differ, because not every patient keeps a long disease. The second and the third can also differ, because old patients began before these three months. This difference falls on the general health of the population.
Worked exampleExample
Question: A child has loose motions. The immediate cause is a virus and the water was dirty. Name both kinds of cause.
Answer: The virus is the immediate cause. Dirty water and a weak body are contributory causes. Not every child who gets dirty water falls ill, because the contributory conditions differ.
10-second revision
- A cold is acute, elephantiasis is chronic
- The three-month count and the total of patients can differ
- The immediate cause and the contributory cause are different
Board tip · BSEBBoard tip
An acute-chronic answer is incomplete without the duration.
Board tip · CBSEBoard tip
In the loose-motions answer keep the virus in a different line from the contributory water.
Check your understandingall correct = mastery ★
1
A common cold is —
💡 Hint:
A short time.
Explanation:
A cold is an acute disease.
2
A chronic disease weighs on health for longer than an acute disease.
Explanation:
True — the long duration also pulls down earnings and study.
3
Elephantiasis is a ______ disease.
💡 Hint:
Long.
Explanation:
Chronic.
4
What are the three counts in Activity 13.4?
Model answer (board format)
Acute patients of the last three months, new chronic patients in the same period, and all the chronic patients of the neighbourhood.
Check your answer:
Infectious agents — Activity 13.5
संक्रामक कारक — क्रियाकलाप 13.5 · Sections 13.2.5–13.3.1 · Activity 13.5
Five groups, five kinds of treatmentNotes
An infectious disease is caused by some other organism. The groups are: viruses, bacteria, fungi, protozoa and worms. The group matters because treatment acts on a life process that belongs to that group.
Viruses: cold, influenza, dengue, AIDS. Bacteria: typhoid, cholera, tuberculosis, anthrax. Many skin infections are caused by fungi. Malaria and kala-azar are caused by protozoa. Intestinal worms and elephantiasis are caused by worms.
A peptic ulcer was long blamed only on lifestyle. Marshall and Warren showed the bacterium Helicobacter pylori. The 2005 Nobel prize was for this work. A short antibiotic treatment works.
Activity 13.5 — a cold and antibioticsActivity
In class, ask how many recently had a cold, a cough or a fever, how many days the illness lasted, how many took an antibiotic, and whether the duration differs between the two groups.
Penicillin blocks the cell wall of bacteria. A human cell does not make a cell wall, so this effect does not fall on us. Viruses do not make that wall. A cold is usually caused by a virus, so antibiotics do not shorten it. Do not take these medicines without a doctor.
Worked exampleExample
Question: Which group does the agent of malaria belong to, and which the agent of a cold?
Answer: Malaria is caused by a protozoan. A cold is caused by a virus. So the two are not treated as one tablet.
10-second revision
- Five groups: virus, bacterium, fungus, protozoan, worm
- Penicillin blocks the cell wall
- Helicobacter pylori in an ulcer
Board tip · BSEBBoard tip
AIDS is a virus and malaria is a protozoan. Do not join them in one line.
Board tip · CBSEBoard tip
The answer about antibiotics and a cold should come from Activity 13.5.
Check your understandingall correct = mastery ★
1
The agent of malaria is —
💡 Hint:
Kala-azar is in the same group.
Explanation:
A protozoan.
2
Penicillin harms a human by breaking the wall of a human cell.
Explanation:
False — a human cell does not make a cell wall. The effect is on bacteria.
3
Cholera is caused by ______.
💡 Hint:
Typhoid is in the same group.
Explanation:
Bacteria.
4
Antibiotics often do not work on a common cold because —
💡 Hint:
Activity 13.5.
Explanation:
Viruses do not make a cell wall.
5
Name the five infectious groups and one disease of each.
Model answer (board format)
Virus: a cold. Bacterium: cholera. Fungus: a skin infection. Protozoan: malaria. Worm: elephantiasis.
Check your answer:
6
A peptic ulcer is caused only by stress, not by any bacterium.
Explanation:
False — Helicobacter pylori is the cause. Marshall and Warren received the Nobel prize in 2005.
The paths of spread
फैलने के रास्ते · Section 13.3.2 · air, water, vector
The path of a communicable diseaseNotes
Microbes that pass from one person to another make communicable diseases. A cold, pneumonia and tuberculosis spread by air. Drops from a sneeze reach a person standing nearby. A crowd and a closed room raise the risk.
Cholera spreads by water when stool mixes with drinking water. Syphilis and AIDS spread by sexual contact. They do not spread by a handshake, a hug or wrestling. The AIDS virus can also go from blood to blood, and to a baby during pregnancy or through milk.
If another animal carries the agent from a sick person to the next host, it is a vector. The most common vector is the mosquito. The female needs blood for her eggs.
Worked exampleExample
Question: Why are the paths of cholera and a common cold different?
Answer: A cold travels in the air by drops from a sneeze. Cholera travels in water mixed with stool. The path is different, so prevention is also different: less crowding for air, and a safe supply for water.
10-second revision
- Air: cold, pneumonia, tuberculosis
- Water: cholera
- The common example of a vector is the mosquito
Board tip · BSEBBoard tip
Write three paths of AIDS: sexual contact, blood, mother to baby. Not a handshake.
Board tip · CBSEBoard tip
A vector is not itself the name of the disease. It carries the agent.
Check your understandingall correct = mastery ★
1
Cholera mainly spreads —
💡 Hint:
A gut disease.
Explanation:
Water mixed with stool spreads cholera.
2
AIDS spreads by a handshake.
Explanation:
False — not by ordinary touch. Sexual contact, blood, or mother to baby.
3
A mosquito is a ______, because it carries the agent to another person.
💡 Hint:
The animal in between.
Explanation:
A vector.
4
A group that spreads by air is —
💡 Hint:
Drops from a sneeze.
Explanation:
A cold, pneumonia and tuberculosis spread by air.
5
Write four paths of communicable disease.
Model answer (board format)
Air, water, sexual contact and a vector. AIDS also spreads by blood.
Check your answer:
Prevention and treatment — Activity 13.6
रोकथाम और उपचार — क्रियाकलाप 13.6 · Sections 13.3.4–13.3.5 · Activity 13.6
Symptoms and the cause, bothNotes
Treatment has two paths. The first is to reduce the effect: medicine for fever, pain or loose motions, and rest in bed so that energy goes into healing. Bland nourishing food belongs here. This path does not kill the microbe.
The second path is to kill the cause. An antibiotic works on bacteria. The same tablet does not work on a virus. Pressing only the symptoms does not cure the disease.
Prevention includes public cleanliness: less crowding, treated water, and no place for mosquitoes to breed. We meet infections every day, but not everyone falls ill, because the immune system often wins.
Activity 13.6 — children under fiveActivity
Take ten well-off families and ten poor families. Both should have children under five. Measure the height and the age of each child. Draw a graph of both groups.
If there is a difference, nutrition and repeated infections can be the cause. If there is no difference, do not decide that poverty is unrelated to health. The sample can be small. After general prevention, the specific prevention is preparing the immune system.
Worked exampleExample
Question: Why does tuberculosis not end even after a fever medicine?
Answer: The fever medicine reduces a symptom. The cause of tuberculosis is a bacterium. Until that cause is killed by an antibiotic, the disease remains. Rest and nourishing food save energy, but they are not the cure by themselves.
10-second revision
- Reducing symptoms is half the path of treatment
- Killing the cause is the other half
- Public cleanliness is general prevention
Board tip · BSEBBoard tip
In an answer on the two principles, write both rest and an antibiotic.
Board tip · CBSEBoard tip
In 13.6 the graph is of height and age. Do not change it into a weight graph.
Check your understandingall correct = mastery ★
1
A fever medicine alone —
💡 Hint:
The first principle.
Explanation:
The symptom falls. The microbe does not die by itself.
2
Stopping mosquitoes from breeding is public hygiene.
Explanation:
True — general prevention of a vector disease.
3
During illness we are told to take bland ______ food.
💡 Hint:
Energy for healing.
Explanation:
Nourishing.
4
Activity 13.6 measures —
💡 Hint:
Two kinds of families.
Explanation:
A graph of height and age.
5
Write the two principles of treatment of an infectious disease.
Model answer (board format)
Reduce the symptoms and the effect, such as rest and a fever medicine. Kill the cause, such as an antibiotic for bacteria.
Check your answer:
6
If one child in class has a cold, every nearby child must fall ill.
Explanation:
False — the immune system often stops an infection from becoming disease.
Immunisation — Activity 13.7
टीकाकरण — क्रियाकलाप 13.7 · Section 13.3.5 · Activity 13.7
An immune system prepared in advanceNotes
General cleanliness is the same for every disease. Specific prevention matches one disease. Immunisation gives the body a weak or killed introduction to that disease in advance, so that a later real infection does not become disease.
In an older method, crusts of smallpox were put on healthy skin. Edward Jenner saw that milkmaids who had been through cowpox were spared smallpox. Cowpox is a mild disease. Cow is vacca in Latin, and from that came vaccinia and the word vaccine.
Vaccines for tetanus, diphtheria, whooping cough, measles and polio are in the public childhood programme. The programme works only when it reaches every child.
Activity 13.7 — rabiesActivity
The rabies virus spreads by the bite of an infected dog or another animal. There are vaccines for both humans and animals. Ask about the local plan: stray dogs, the vaccine after a bite, and where a bite is reported.
If the plan is not enough, write an improvement. Which immunisations run at the nearby health centre, and which diseases are the large ones in your area, are also part of the list.
Worked exampleExample
Question: How did Jenner’s trial protect against smallpox?
Answer: He gave people the mild disease cowpox. The smallpox virus is close to it, so the body became ready for smallpox too. That is the principle of a vaccine.
10-second revision
- A vaccine is disease-specific prevention
- Jenner and cowpox
- Rabies spreads by a bite
Board tip · BSEBBoard tip
In the vaccine list write all five names: tetanus, diphtheria, whooping cough, measles, polio.
Board tip · CBSEBoard tip
Rabies is a virus. Do not change the answer by writing bacterium.
Check your understandingall correct = mastery ★
1
The start of the smallpox vaccine is linked with —
💡 Hint:
Vacca.
Explanation:
Jenner saw resistance to smallpox from cowpox.
2
The polio vaccine is in the childhood immunisation programme.
Explanation:
True — tetanus, diphtheria, whooping cough, measles and polio are listed.
3
Rabies spreads by the bite of an infected ______.
💡 Hint:
Activity 13.7.
Explanation:
An infected dog or another animal.
4
Define immunisation. Give one example.
Model answer (board format)
Immunisation prepares the body immune system in advance for one disease. An example is the polio or measles vaccine.
Check your answer:
❓ Full question bank — with answers and explanations — 66 questions
Pick a type. The 30 lesson checks are separate — each lesson has as many as its topic needs. All correct earns mastery ★.
BSEB modelpractice · not annual60 tried · 0 correctMultiple choiceMCQ130 tried · 0 correctTrue / falseTrue / false80 tried · 0 correctFill in the blanksFill80 tried · 0 correctMatchMatch20 tried · 0 correctAssertion–reasonAssertion–reason50 tried · 0 correctBalancingBalancing40 tried · 0 correctIdentifyIdentify20 tried · 0 correctShort and longVSA, SA, LA120 tried · 0 correctCBSE-stylenot a PYQ60 tried · 0 correct
No question is marked as a verified past paper. The BSEB set is a model for practice. CBSE items are CBSE-style, not a copy of any year’s paper.
Multiple choice
0/13Pick one option.
1
It is not enough for complete health —
💡 Hint:
Being well is different.
Explanation:
Freedom from disease alone is not complete health.
2
Elephantiasis is —
💡 Hint:
Long.
Explanation:
Chronic, caused by a worm.
3
The agent of dengue is —
💡 Hint:
In the cold group.
Explanation:
A virus.
4
Anthrax is caused by —
💡 Hint:
The typhoid group.
Explanation:
Bacteria.
5
Kala-azar is caused by —
💡 Hint:
The malaria group.
Explanation:
A protozoan.
6
Penicillin blocks —
💡 Hint:
Our cells do not make a wall.
Explanation:
The bacterial wall.
7
Tuberculosis spreads mainly by —
💡 Hint:
A sneeze.
Explanation:
Air.
8
Syphilis spreads —
💡 Hint:
Not ordinary touch.
Explanation:
By sexual contact.
9
An example of a vector is —
💡 Hint:
The female needs blood.
Explanation:
A mosquito.
10
The second principle of treatment is —
💡 Hint:
The first is the symptom.
Explanation:
Killing the cause.
11
Jenner used, to protect against smallpox —
💡 Hint:
A mild disease.
Explanation:
Cowpox.
12
Rabies spreads —
💡 Hint:
Activity 13.7.
Explanation:
By a bite.
13
Helicobacter pylori is linked with —
💡 Hint:
2005.
Explanation:
A peptic ulcer.
True or false
0/81
Clean water can be a condition of good health.
Explanation:
True — Activity 13.2.
2
The difference between acute and chronic is only the colour of the agent.
Explanation:
False — the difference is duration.
3
Many skin infections are caused by fungi.
Explanation:
True.
4
Antibiotics always end every cold in one day.
Explanation:
False — a cold is usually caused by a virus.
5
Crowding increases airborne disease.
Explanation:
True — drops reach people nearby.
6
A symptom medicine by itself kills the microbe.
Explanation:
False — the cause has to be killed separately.
7
An immunisation programme is useful only when it reaches all children.
Explanation:
True.
8
AIDS spreads only by air.
Explanation:
False — sexual contact, blood, or mother to baby.
Fill in the blanks
0/81
A disease of short duration is called ______.
💡 Hint:
Acute.
Explanation:
A cold.
2
A disease of long duration is called ______.
💡 Hint:
Chronic.
Explanation:
Elephantiasis.
3
The agent of AIDS is a ______.
💡 Hint:
A virus.
Explanation:
Not a bacterium.
4
The agent of tuberculosis is a ______.
💡 Hint:
A bacterium.
Explanation:
It spreads by air.
5
The antibiotic that blocks the cell wall is ______.
💡 Hint:
Penicillin.
Explanation:
This effect is not on humans.
6
The mild disease that protected against smallpox was ______.
💡 Hint:
Cowpox.
Explanation:
Jenner.
7
An animal that carries the agent is called a ______.
💡 Hint:
A vector.
Explanation:
A mosquito.
8
The ulcer bacterium is named Helicobacter ______.
💡 Hint:
Pylori.
Explanation:
Nobel 2005.
Match
0/21
Match the disease with the agent.
Column B: A. Protozoan · B. Virus · C. Worm · D. Bacterium
1. Cholera
2. Malaria
3. AIDS
4. Elephantiasis
Explanation:
Cholera is a bacterium, malaria a protozoan, AIDS a virus, elephantiasis a worm.
2
Match the disease with its path.
Column B: A. Water · B. Sexual contact · C. Vector · D. Air
1. Common cold
2. Cholera
3. Syphilis
4. Malaria
Explanation:
A cold by air, cholera by water, syphilis by sexual contact, malaria by a vector.
Assertion–reason
0/51
Assertion (A): A common cold is an acute disease.
Reason (R): It lasts a short time.
Explanation:
Both are true and R is the reason.
2
Assertion (A): Penicillin stops a bacterium from building a wall.
Reason (R): Malaria is caused by a protozoan.
Explanation:
Both are true, but R does not explain penicillin.
3
Assertion (A): Airborne diseases can increase in a crowd.
Reason (R): AIDS spreads by a handshake.
Explanation:
A is true. R is false.
4
Assertion (A): A fever medicine alone kills the tuberculosis bacterium.
Reason (R): Killing the cause is a separate principle of treatment.
Explanation:
A is false. R is true.
5
Assertion (A): Cowpox became a preparation against smallpox.
Reason (R): The two viruses are close.
Explanation:
Both are true and R explains A.
Coefficient practice
0/4These equations are not results of this chapter. They are only coefficient practice on H2 + O2 → H2O.
1
This is coefficient practice. This equation is not a result of this chapter. Balance it by filling coefficients (blank = 1).
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
2
This is coefficient practice. This equation is not a result of this chapter. Balance it by filling coefficients (blank = 1).
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
3
This is coefficient practice. This equation is not a result of this chapter. Balance it by filling coefficients (blank = 1).
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
4
This is coefficient practice. This equation is not a result of this chapter. Balance it by filling coefficients (blank = 1).
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
Classify
0/21
Place each disease as acute or chronic.
Common cold
Elephantiasis
A fever of one or two days that ends
An infection that runs for years
Explanation:
A cold and a short fever are acute. Elephantiasis and an infection of many years are chronic.
2
Place each disease in its agent group.
Influenza
Typhoid
Malaria
Dengue
Explanation:
Influenza and dengue are viruses, typhoid is a bacterium, malaria is a protozoan.
Very short answer
0/51
Write the meaning of health in one line.
Model answer (board format)
Being well and being able to function properly.
Check your answer:
2
Write one difference between acute and chronic.
Model answer (board format)
Acute lasts a short time, chronic lasts a long time.
Check your answer:
3
What is a vector? Give one example.
Model answer (board format)
An animal that carries the agent from one person to another is a vector. An example is the mosquito.
Check your answer:
4
What is immunisation?
Model answer (board format)
Preparing the immune system in advance for a disease.
Check your answer:
5
Why does penicillin not harm a human in the same way?
Model answer (board format)
It blocks the bacterial cell wall. A human cell does not make a cell wall.
Check your answer:
Short answer
0/41
Write three paths of communicable disease with examples.
Model answer (board format)
A cold by air, cholera by water, malaria by the mosquito vector.
Check your answer:
2
Write the two principles of treatment with examples.
Model answer (board format)
Reduce symptoms, such as fever medicine and rest. Kill the cause, such as an antibiotic for bacteria.
Check your answer:
3
How did Jenner’s observation become the idea of a vaccine?
Model answer (board format)
People who had been through cowpox were spared smallpox. A mild related virus prepares the body.
Check your answer:
4
What is learned from Activity 13.5 about antibiotics and a cold?
Model answer (board format)
A cold is usually caused by a virus, so the duration need not differ between those who took an antibiotic and those who did not.
Check your answer:
Long answer
0/31
Write the difference between health and disease. Add one example each of acute and chronic, and one public-health measure.
Model answer (board format)
Health is functioning well. Disease is some part stopping its work. A cold is acute and elephantiasis is chronic. Clean drinking water is a public measure.
Check your answer:
2
Write the five agent groups with examples. On which group does an antibiotic work, and why not on a cold?
Model answer (board format)
Virus: a cold. Bacterium: cholera. Fungus: skin. Protozoan: malaria. Worm: elephantiasis. An antibiotic blocks the bacterial wall. A cold is caused by a virus, so that tablet does not shorten it.
Check your answer:
3
In one answer write the chain of spread, the two principles of treatment, and one example of immunisation.
Model answer (board format)
The next person falls ill from a sick person through air, water or a vector. Treatment reduces symptoms and kills the cause. The polio vaccine prepares the immune system in advance.
Check your answer:
BSEB model paper · practice
0/6This model set is for practice. It is not a question from any year’s annual examination.
1
Kala-azar and malaria are both —
💡 Hint:
One group.
Explanation:
Protozoa.
2
The childhood programme includes —
💡 Hint:
Five names in the list.
Explanation:
Polio.
3
The diphtheria vaccine is part of the ______ programme.
💡 Hint:
Childhood immunisation.
Explanation:
Public.
4
Write one example of a contributory cause.
Model answer (board format)
Dirty drinking water or weak nutrition. The immediate cause can separately be a microbe.
Check your answer:
5
This is coefficient practice. This equation is not a result of this chapter. Balance H2 + O2 with H2O. A blank means 1.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
6
In one sentence each, what do Activities 13.1, 13.4 and 13.7 ask?
Model answer (board format)
13.1 asks for the immediate and later health effects of a disaster. 13.4 asks for the counts of acute and chronic disease. 13.7 asks for the local plan against rabies.
Check your answer:
CBSE-style questions
0/6These are competency-based practice questions. They are not copies of a CBSE paper.
1
After cholera in a village, people take only a fever tablet and the well stays the same. The best next step is —
💡 Hint:
Two principles and the water.
Explanation:
A symptom tablet does not remove the cause. The water path has to be closed.
2
Half the class took an antibiotic for a cold and the duration did not fall. The most reasonable conclusion is —
💡 Hint:
Activity 13.5.
Explanation:
That tablet does not work on a virus.
3
Assertion (A): A difference in height between poor and well-off children can be tied to nutrition.
Reason (R): Repeated infection and less food can hold back growth.
Explanation:
Both are true and R explains A.
4
Assertion (A): Rabies vaccines are described for both humans and animals.
Reason (R): Rabies spreads by an ordinary handshake.
Explanation:
A is true. R is false — it spreads by a bite.
5
A neighbourhood has mosquitoes, open drinking water and children without vaccines. Write three separate measures.
Model answer (board format)
Stop water from collecting so mosquitoes do not breed. Boil or treat water so cholera stops. Complete polio and measles vaccines for the children.
Check your answer:
6
A student says that a person is healthy if there is no disease. Answer using Activity 13.2.
Model answer (board format)
Having no disease is not enough. If clean water does not reach every home, people can remain unwell even when they seem free of disease. Health means functioning well.
Check your answer:
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What you learned
- Health is working well. Having no disease is not the whole of health.
- An acute disease is short and a chronic disease is long and heavier.
- The agent can be a virus, a bacterium, a fungus, a protozoan or a worm.
- Spread is by air, water, sexual contact or a vector such as a mosquito.
- Treatment both reduces symptoms and kills the cause. Antibiotics do not kill viruses.
- Prevention includes both public cleanliness and immunisation.
| What | Keep this |
|---|---|
| Acute | short, such as a cold |
| Chronic | long, such as elephantiasis |
| Virus | cold, influenza, dengue, AIDS |
| Bacteria | typhoid, cholera, TB, anthrax |
| Vector | mosquito |
| Vaccines | tetanus, diphtheria, whooping cough, measles, polio |
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