Health and Hygiene ICSE Class 9: Diseases, Their Spread and Control, Aids to Health and Health Organisations

What Health and Hygiene is about

Weightage: CISCE publishes no chapter weightage for ICSE Biology. Health and Hygiene is topic 7, Health and Hygiene, of the Class IX part of the 2028 syllabus; the Class IX paper (80 marks, 2 hours) is set and marked by the school.Source: CISCE ICSE Biology (Science Paper 3) syllabus, examination year 2028 (Class IX)

Key concepts

Types of disease

Communicable (infectious) diseases are caused by germs (pathogens): bacteria, viruses, protozoa or worms, and spread from one person to another. Examples: cholera, tuberculosis, malaria, chicken pox.

Non-communicable diseases are not caused by germs and do not spread from person to person; they result from faulty diet, lifestyle, heredity, age or the environment. Examples: diabetes, heart disease, cancer, high blood pressure, deficiency diseases like rickets.

By how widely and how often a disease occurs:

Term	Meaning	Example
Endemic	always present at a low level in a particular region	malaria in some forest regions; goitre in iodine-poor hilly areas
Epidemic	sudden outbreak affecting many people in a region at the same time	cholera after floods; a dengue outbreak in a city
Pandemic	an epidemic that spreads across countries and continents	COVID-19; the influenza of 1918
Sporadic	occurs occasionally, in scattered cases	tetanus; occasional cases of plague

Worked example

Classify: (a) a few cases of tetanus in a district over a year, (b) hundreds of cholera cases in a town after a flood, (c) goitre that has always been common in a hill district.

Try it first, then show the solutionSolution

1. (a) Scattered, occasional: sporadic.
2. (b) Sudden, many in one region: epidemic.
3. (c) Always present in a region: endemic.

Answer: Sporadic, epidemic, endemic.

Modes of transmission

Through air: an infected person coughs, sneezes or talks, releasing droplets with germs that others breathe in. Examples: tuberculosis, chicken pox, common cold, influenza.

Through water and food: germs from the faeces of patients reach drinking water or food. Examples: cholera, typhoid, hepatitis A, amoebic dysentery, ascariasis.

Through vectors (animals that carry germs):

• Housefly: sits on faeces and garbage, then on food, carrying germs on its hairy legs and body and in its vomit and droppings: cholera, typhoid, dysentery, diarrhoea.
• Mosquito: female Anopheles spreads malaria; Culex spreads filariasis; Aedes spreads dengue. Germs pass into the blood when the mosquito bites.
• Cockroach: lives in drains and kitchens, contaminating food and utensils: cholera, typhoid, dysentery, diarrhoea.

Other routes: direct contact, sexual contact, blood (transfusion, shared needles), mother to baby, bites of animals (rabies), and contaminated soil (tetanus).

Worked example

Why is the housefly called a mechanical carrier of disease?

Try it first, then show the solutionSolution

1. The germs do not grow inside the fly.
2. It simply carries them on its legs and body from filth to food.

Answer: It carries germs physically, without being infected.

Bacterial diseases: cholera, typhoid, tuberculosis

Disease	Spread by	Symptoms	Control
Cholera	contaminated water and food; houseflies, cockroaches	sudden, severe watery diarrhoea ('rice-water' stools), vomiting, rapid dehydration, muscle cramps	ORS (oral rehydration solution) at once; drink boiled or chlorinated water; cover food; proper sewage disposal; vaccination
Typhoid	contaminated water and food; flies; carriers	prolonged high fever (rising step by step), headache, weakness, abdominal pain, loss of appetite; sometimes rose-coloured spots	safe water and food; washing hands; antibiotics under a doctor; typhoid vaccine
Tuberculosis (TB)	air (droplets from coughing patients)	persistent cough for more than two weeks, blood in sputum, evening fever, night sweats, loss of weight, chest pain	BCG vaccine in infancy; complete course of medicines (DOTS); good ventilation; covering mouth when coughing; good diet

Worked example

Why is ORS the first treatment for a cholera patient?

Try it first, then show the solutionSolution

1. Cholera causes rapid loss of water and salts through diarrhoea and vomiting.
2. Dehydration can kill quickly.
3. ORS (water, salts and sugar) replaces the lost water and salts.

Answer: It prevents death from dehydration.

Viral diseases: AIDS, chicken pox, hepatitis

Disease	Spread by	Symptoms	Control
AIDS (acquired immune deficiency syndrome)	unprotected sexual contact, infected blood or blood products, shared needles, infected mother to baby. Not by touching, hugging, sharing food, or mosquitoes	weakens the immune system: long-lasting fever, loss of weight, diarrhoea, swollen lymph nodes, repeated infections (e.g. TB, pneumonia)	safe sex, screened blood, sterile, disposable needles, awareness; medicines slow it but there is no cure or vaccine
Chicken pox	air and direct contact with blisters	fever, tiredness, then itchy rash of red spots that become fluid-filled blisters and form scabs	isolate the patient until scabs fall off; avoid scratching; vaccine available
Hepatitis (inflammation of the liver)	Hepatitis A: contaminated water and food. Hepatitis B: blood, needles, sexual contact, mother to baby	jaundice (yellow eyes and skin), dark yellow urine, loss of appetite, nausea, fatigue, pain over the liver	safe water and food (A); screened blood, sterile needles (B); vaccines for A and B; rest and light diet

Worked example

Can AIDS spread by shaking hands or by mosquito bites? Explain.

Try it first, then show the solutionSolution

1. The virus spreads only through blood, sexual fluids and from mother to baby.
2. It does not survive outside the body for long and is not passed on by touch.
3. Mosquitoes do not transmit it.

Answer: No to both.

Protozoan and helminthic diseases

Protozoan diseases (single-celled animal-like parasites):

Disease	Spread by	Symptoms	Control
Malaria	bite of an infected female Anopheles mosquito	fever with chills and shivering, returning every 1-3 days, sweating as the fever falls, headache, anaemia, enlarged spleen	prevent mosquito breeding (drain stagnant water, oil on ponds, fish that eat larvae); mosquito nets, repellents; antimalarial medicines
Amoebic dysentery	contaminated food and water; flies	abdominal pain, frequent stools with mucus and blood	safe water, washed and covered food, hygiene, proper sanitation
Sleeping sickness	bite of the tsetse fly (Africa)	fever, swollen lymph glands, then extreme drowsiness, confusion; can be fatal	control tsetse flies (clearing bushes, traps); protective clothing; medicines

Helminthic diseases (parasitic worms):

Disease	Spread by	Symptoms	Control
Ascariasis (roundworm)	eggs in contaminated soil, food, water; unwashed vegetables, dirty hands	abdominal pain, indigestion, malnutrition, slow growth in children; heavy infection can block the intestine	wash hands and vegetables; use latrines; deworming medicine
Taeniasis (tapeworm)	eating raw or undercooked pork or beef with tapeworm cysts	abdominal pain, loss of weight, indigestion; worm segments in stools	eat well-cooked meat; meat inspection; sanitation
Filariasis (elephantiasis)	bite of the Culex mosquito carrying worm larvae	fever, swelling of the legs, arms or other parts (lymph vessels blocked), thick skin	mosquito control; nets; mass medicine programmes

Worked example

Which two diseases in this list are spread by mosquitoes, and which kind of mosquito spreads each?

Try it first, then show the solutionSolution

1. Malaria: female Anopheles.
2. Filariasis: Culex.

Answer: Malaria (Anopheles) and filariasis (Culex).

Aids to health and the local defence system

• Vaccination: giving a vaccine (killed or weakened germs, or their toxoid) by injection or mouth.
• Immunisation: the process of making a person immune to a disease, usually by vaccination; the body makes its own antibodies and memory, giving lasting protection. (National immunisation schedules give BCG, polio, DPT, measles and other vaccines.)
• Antitoxin: an antibody that neutralises a toxin made by germs (e.g. tetanus or diphtheria antitoxin).
• Serum: the fluid part of blood; an antiserum contains ready-made antibodies or antitoxins, usually prepared in horses, giving quick, short-term protection (e.g. anti-tetanus serum, anti-snake-venom).
• Antiseptics: chemicals applied to living tissues (skin, wounds) to kill or stop the growth of germs; mild. Examples: Dettol, tincture of iodine, hydrogen peroxide, boric acid, spirit (alcohol).
• Disinfectants: stronger chemicals used on non-living things (floors, toilets, drains, instruments) to kill germs. Examples: phenol, bleaching powder, formalin, lime.
• Antibiotics: medicines obtained from microbes that kill or stop bacteria: penicillin, streptomycin. They do not work against viruses and must be taken only on a doctor's advice, for the full course.

Local defence system (the body's first line of defence):

• Skin: a tough, dead outer layer that germs cannot cross; sweat and sebum discourage germs.
• Mucous membranes of the nose and windpipe trap germs in mucus, and cilia sweep them out; nose hairs filter air.
• Tears and saliva contain lysozyme, which kills bacteria.
• Hydrochloric acid of the stomach kills germs in food.
• If germs enter a wound: blood clotting seals it, and inflammation brings white blood cells that engulf germs (phagocytosis); pus is dead WBCs and germs.

Merits: it acts at once against all kinds of germs, keeps most germs out, and needs no previous exposure.

Worked example

Why should Dettol be used on a cut but bleaching powder used in a drain?

Try it first, then show the solutionSolution

1. Dettol is an antiseptic, mild enough for living tissue.
2. Bleaching powder is a strong disinfectant that would damage skin, but is fine for non-living surfaces.

Answer: Antiseptic for skin; disinfectant for objects.

Health organisations: Red Cross and WHO

International Red Cross:

• Founded by Henry Dunant of Switzerland (1863), after seeing the suffering of wounded soldiers; headquarters at Geneva. Emblem: a red cross on a white background.
• Major activities: care of the wounded and sick in wars, including prisoners of war; relief during disasters (floods, earthquakes, famines): food, shelter, medicines; blood banks and blood donation drives; first-aid training and ambulance services; maternity and child welfare; tracing missing persons.

World Health Organisation (WHO):

• An agency of the United Nations set up on 7 April 1948 (celebrated as World Health Day); headquarters at Geneva.
• Major activities: control and eradication of communicable diseases (it led the eradication of smallpox and campaigns against polio, malaria and TB); support for immunisation programmes; setting international health standards for medicines and food; health education and research; collecting and sharing disease data and warning about epidemics and pandemics; helping countries improve health services, sanitation and nutrition.

Worked example

Give two activities each of the Red Cross and WHO.

Try it first, then show the solutionSolution

1. Red Cross: disaster relief; blood banks (or first-aid training, help to war victims).
2. WHO: control of epidemics and immunisation; setting health standards (or research, health education).

Answer: As above.

Health and Hygiene in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Common Diseases: Bacterial, Viral, Protozoan and Helminthic
• Modes of Transmission, Body Defences and Health Organisations

Health and Hygiene: key facts

Disease spread terms

$\text{sporadic (scattered)},\text{endemic (always, one region)},\text{epidemic (sudden, one region)},\text{pandemic (worldwide)}$

By scale and pattern.

Vectors

$\text{housefly, cockroach}\to \text{food-borne};\text{Anopheles}\to \text{malaria};\text{Culex}\to \text{filariasis}$

Also tsetse fly → sleeping sickness.

Antiseptic versus disinfectant

$\text{antiseptic: living tissue};\text{disinfectant: non-living objects}$

Disinfectants are stronger.

Vaccine versus serum

$\text{vaccine}\to \text{own antibodies (slow, lasting)};\text{serum}\to \text{ready antibodies (quick, short)}$

Immunisation.

Health and Hygiene: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the school exam asks Health and Hygiene

The question patterns to expect, and the method that works for each.

Tricks to remember Health and Hygiene

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Three vectors: 'Flies Fetch, Mosquitoes Bite, Cockroaches Crawl'

  Housefly carries germs to food; mosquito injects while biting; cockroach contaminates kitchens.

  Use it when: Vector modes.

• Mosquito pairs

  Anopheles - Ague (malarial fever); Culex - elephant legs (filariasis).

  Use it when: Which mosquito spreads what.

• Bacterial: CTT; Viral: ACH; Protozoan: MAS; Worms: ATF

  Cholera Typhoid TB; AIDS Chicken pox Hepatitis; Malaria Amoebic dysentery Sleeping sickness; Ascariasis Taeniasis Filariasis.

  Use it when: Syllabus disease list.

• Antiseptic for Alive

  AntiSeptic on Skin (alive); Disinfectant on Drains (dead objects).

  Use it when: Antiseptics versus disinfectants.

Health and Hygiene: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section B style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 5-mark question split into 2 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Health and Hygiene

The slips examiners see most often, and what to write instead.

• ✗Mistake: Epidemic and pandemic confused

  Both mean many cases.

  Wrong working

  A cholera outbreak in one town is a pandemic.

  Right working

  Outbreak in a region: epidemic; across countries and continents: pandemic.

  ✓Do this: Pan = all (worldwide).

  Usually costs: 1 mark.

• ✗Mistake: Writing scientific names of germs

  The syllabus does not require them, and wrong ones lose credibility.

  Wrong working

  Long Latin names with spelling errors.

  Right working

  Say 'a bacterium', 'a virus', 'a protozoan', 'a roundworm'; name the vector.

  ✓Do this: Give spread, symptoms and control.

  Usually costs: Time and accuracy.

• ✗Mistake: Wrong mosquito

  All mosquito-borne diseases are linked to one mosquito.

  Wrong working

  Malaria is spread by Culex.

  Right working

  Malaria: female Anopheles; filariasis: Culex.

  ✓Do this: Anopheles = malaria.

  Usually costs: 1 mark.

• ✗Mistake: Myths about AIDS

  Students write casual contact as a mode of spread.

  Wrong working

  AIDS spreads by shaking hands or sharing food.

  Right working

  Only by sexual contact, infected blood, shared needles, and mother to baby.

  ✓Do this: Blood, sex, needles, mother.

  Usually costs: 1 mark.

• ✗Mistake: Antiseptic and disinfectant swapped

  Both kill germs.

  Wrong working

  Phenol is applied to wounds as an antiseptic.

  Right working

  Phenol is a disinfectant for floors and drains; Dettol or iodine on wounds.

  ✓Do this: Antiseptic on the Alive.

  Usually costs: 1 mark.

Practice questions on Health and Hygiene

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   Which disease is spread through air?
   (a) cholera
   (b) tuberculosis
   (c) typhoid
   (d) taeniasis

   Hint

   Droplets.

   Answer

   (b)

2. Q2 · 1 mark · MCQExam level

   Tincture of iodine applied on a wound is an example of:
   (a) disinfectant
   (b) antiseptic
   (c) antibiotic
   (d) vaccine

   Hint

   Living tissue.

   Answer

   (b)

3. Q3 · 2 marks · Very short answerExam level

   Name the type of germ causing: (a) amoebic dysentery, (b) hepatitis, (c) ascariasis, (d) typhoid.

   Hint

   Protozoan, virus, worm, bacterium.

   Answer

   (a) Protozoan (b) Virus (c) Helminth (roundworm) (d) Bacterium

4. Q4 · 2 marks · Short answerExam level

   Give two activities of WHO.

   Hint

   Epidemics; standards.

   Answer

   Controlling and eradicating communicable diseases (e.g. smallpox eradication, immunisation drives); setting international health standards (also research, health education, help to countries).

5. Q5 · 2 marks · Short answerHarder exam level

   How can taeniasis be prevented? Explain why cooking helps.

   Hint

   Cysts in meat.

   Answer

   Eat only well-cooked pork or beef; inspect meat; maintain sanitation. Thorough cooking kills the tapeworm cysts in the meat.

6. Q6 · 3 marks · Short answerHarder exam level

   Explain how a cockroach can spread disease and give two ways of controlling cockroaches at home.

   Hint

   Drains to kitchen.

   Answer

   Cockroaches move between drains, garbage and kitchens, carrying germs on their bodies and leaving droppings on food and utensils (cholera, typhoid, dysentery). Control: keep kitchens clean and dry, store food covered, seal cracks and drains, use baits or insecticides.

7. Q7 · 2 marks · Short answerHarder exam level

   What is meant by immunisation? Why are children given vaccines in a fixed schedule?

   Hint

   Before exposure.

   Answer

   Immunisation is making a person immune to a disease, usually by vaccination, so the body makes its own antibodies. A schedule protects children at the ages when they are most at risk and gives boosters to keep immunity strong.

8. Q8 · 3 marks · Short answerHarder exam level

   Give the mode of spread, two symptoms and one control measure of chicken pox.

   Hint

   Blisters.

   Answer

   Spread through air and contact with blisters. Symptoms: fever; itchy rash of fluid-filled blisters that scab. Control: isolate the patient till scabs fall (vaccination).

9. Q9 · 3 marks · Short answerHarder exam level

   State two merits of the local defence system and give one example where it fails and germs get in.

   Hint

   Immediate, non-specific.

   Answer

   It acts immediately and works against all types of germs (it needs no previous exposure). It fails when the skin is broken by a cut or burn, or when germs are injected by a mosquito bite, letting them past the barrier.

10. Q10 · 3 marks · Short answerHOTS / competency

    A village of 2500 people has about 50 cases of malaria every month all year. A city of 2 000 000 suddenly reports 8000 dengue cases in two weeks. Calculate the percentage affected in each period and classify each situation.

    Hint

    Steady versus sudden.

    Answer

    Village: 50/2500 × 100 = 2% per month, steady all year: endemic. City: 8000/2 000 000 × 100 = 0.4% in two weeks, a sudden outbreak: epidemic.

11. Q11 · 3 marks · Short answerHOTS / competency

    Explain why AIDS patients often die of other infections such as TB or pneumonia rather than of AIDS itself, and suggest two ways to prevent the spread of AIDS.

    Hint

    Immune system.

    Answer

    The AIDS virus destroys white blood cells of the immune system, so the body cannot fight other germs; ordinary infections become severe and fatal. Prevention: safe sex; use of screened blood and sterile disposable needles (also preventing mother-to-child spread with medicines).

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Vector of malaria?Show answer

   Female Anopheles mosquito.

2. 2.Vector of sleeping sickness?Show answer

   Tsetse fly.

3. 3.Vaccine against TB?Show answer

   BCG.

4. 4.A disease always present in a region is called?Show answer

   Endemic.

5. 5.Main symptom of hepatitis?Show answer

   Jaundice (yellow eyes and skin).

6. 6.Example of a disinfectant?Show answer

   Phenol (or bleaching powder).

7. 7.Who founded the Red Cross?Show answer

   Henry Dunant.

8. 8.When is World Health Day?Show answer

   7 April.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you define endemic, epidemic, pandemic and sporadic with examples?
• ☐Can you name the vector of malaria, filariasis and sleeping sickness?
• ☐Can you give two symptoms and two control measures for each of the 12 diseases?
• ☐Can you distinguish antiseptics and disinfectants, vaccines and serums?
• ☐Can you describe the local defence system?
• ☐Can you list activities of the Red Cross and WHO?

Health and Hygiene: frequently asked questions