Health: The Ultimate Treasure — Class 8 Science Chapter 3

Communicable diseases (caused by pathogens, spread from person to person):

• Cold and flu — caused by a virus, spreads through the air.
• Typhoid — caused by bacteria, spreads through contaminated water and food.
• Chickenpox — caused by a virus, spreads through the air and contact.

Non-communicable diseases (not caused by pathogens, do not spread):

• Diabetes — linked to lifestyle, diet and hormonal imbalance.
• Asthma — linked to environment and lifestyle.

Correct answer: (b) (ii) and (iii) — Asthma and Diabetes.

Explanation: Asthma and diabetes are non-communicable — they are not caused by pathogens and do not spread from one person to another. They are linked to lifestyle, diet and/or environment.

Typhoid is communicable, caused by bacteria and spread through contaminated water and food. Measles is communicable, caused by a virus and spread through the air. So options (a), (c) and (d) are incorrect because each includes at least one communicable disease.

(i) Immediate actions the school should take:

• Advise students showing symptoms to stay at home and rest — this helps the body recover and minimises spreading the disease to others.
• Ask everyone to cover the mouth and nose while coughing or sneezing, and to use masks in crowded areas like the assembly hall and classrooms.
• Ensure soap and water are available at every washbasin and encourage frequent handwashing.
• Tell students not to share personal items such as handkerchiefs, water bottles, tiffin boxes or pencils.
• Clean and disinfect frequently touched surfaces such as desks, door handles and taps.
• Improve ventilation by keeping windows open so fresh air circulates.
• Inform parents and, if the outbreak is large, consult the local health authorities.

(ii) Responding considerately to a classmate showing symptoms:

• Speak kindly and privately, never in front of the whole class, and never tease or avoid them in an obvious way.
• Say something caring such as, “You don’t look well — you should rest at home and get better soon.”
• Offer practical help — share notes with them, or tell the class teacher so they can inform the parents.
• Politely suggest they use a mask or handkerchief, framing it as concern for them, not disgust.
• Remember they are unwell, not at fault. Anyone can catch flu, and it could easily be you next.

(iii) Protecting yourself and others:

• Wash hands with soap and water frequently, especially before eating.
• Wear a mask in the crowded classroom.
• Avoid touching your eyes, nose and mouth with unwashed hands.
• Do not share water bottles, food or personal items.
• Sit at a slight distance from someone coughing, if seating allows.
• Keep your own immunity strong — eat well, sleep enough and stay active.
• If you develop symptoms yourself, stay home rather than spreading it further.

(i) Precautions before, during and after the trip:

Before:

• Consult a doctor about preventive medicines and check any health advisories for that region.
• Pack mosquito repellent, mosquito nets and long-sleeved clothes.
• Find out whether the area has a peak season for malaria, such as after the monsoon.

During:

• Sleep under a mosquito net, especially at night.
• Wear long-sleeved clothes and full trousers, particularly at dawn and dusk.
• Apply mosquito repellent on exposed skin.
• Keep doors and windows closed or screened; avoid areas with still water where mosquitos breed.
• Ensure the place you stay has no stagnant water in coolers, pots or tyres nearby.

After:

• Watch for symptoms — high fever, profuse sweating and periodic chills — for several weeks after returning.
• If any appear, see a doctor immediately and mention the travel history, since early diagnosis matters.
• Do not self-medicate with leftover medicines.

(ii) Explaining mosquito nets and repellents to a younger sibling:

You could say: “Malaria doesn’t spread by touching someone or sharing food — it spreads only through a mosquito bite. The mosquito is like a tiny carrier that picks up the germ from a sick person and injects it into the next person it bites. So if we stop the mosquito from biting us, we simply cannot get malaria. The net is like a shield around your bed at night, and the repellent is like an invisible coat that keeps mosquitos away from your skin. Wearing full-sleeved clothes gives them less skin to land on.”

(iii) What could happen if travellers ignore health advisories:

• They may fall seriously ill with high fever, sweating and chills, which can become severe if untreated.
• Illness could ruin the trip and require hospitalisation far from home.
• They could carry the disease back to their own city. If local mosquitos bite them, malaria could begin spreading in a place where it was previously rare.
• Children and elderly travellers are at greater risk of complications.
• Delayed diagnosis is likely, because doctors at home may not suspect malaria unless told about the travel.

(i) What you could say to him, without being rude:

• Speak from care, not accusation: “Uncle, I read in my science chapter that tobacco raises the risk of cancer. I care about you and I don’t want you to get ill.”
• Mention Kamal Ranadive’s research, which showed how tobacco, diet and pollution can raise the risk of cancer.
• Point out that smoking harms the family too, since others breathe the smoke.
• Frame it around friendship pressure: “Real friends won’t think less of you if you say no.”
• Offer support rather than a lecture — suggest he speak to a doctor, and encourage healthier ways to relax such as walking, yoga or pranayama.
• Avoid scolding or shaming, which usually makes people defensive rather than willing to change.

(ii) If a friend offers you a cigarette at a party:

• Say no clearly and politely — “No thanks, I don’t smoke.” A simple, confident refusal works best.
• You need not justify yourself, but you can add a light reason: “It’s bad for my fitness” or “My asthma acts up.”
• Change the subject or move to another group.
• Remember that the chapter says clearly: say ‘NO’ to harmful substances like tobacco, alcohol, and addictive drugs.
• If a friend keeps pressuring you, that pressure itself says something about the friendship.
• Tell a trusted adult if you are being repeatedly pressured.

(iii) How schools can help prevent such harmful habits:

• Run awareness programmes showing the real health effects of tobacco, alcohol and drugs.
• Invite doctors to speak to students and answer their questions directly.
• Teach refusal skills — how to say no confidently when pressured by peers.
• Provide counsellors students can talk to privately, as happened for the boy in Activity 3.1.
• Encourage sports, yoga and cultural activities so students have healthy outlets and belong to positive groups.
• Maintain a strict tobacco-free campus so that teachers and staff model the behaviour.
• Organise poster, debate and street-play competitions on the dangers of addiction.
• Involve parents through awareness meetings, since habits often begin at home.

Vinita could ask Saniya the following questions:

• “If antibiotics cure any infection, why doesn’t the doctor give them for a common cold or flu?” — This leads Saniya to see that antibiotics work only against bacterial infections. Colds, flu, dengue, chickenpox and measles are caused by viruses, and antibiotics do not work against them.
• “Malaria is an infection — is it caused by bacteria?” — Malaria is caused by protozoa, and antibiotics do not work against diseases caused by protozoa either.
• “What about ascariasis, caused by worms? Would an antibiotic kill a roundworm?” — Another pathogen type antibiotics do not target.
• “Have you heard about antibiotic resistance in the news?” — This raises the key danger: bacteria that were earlier killed by an antibiotic now survive and multiply despite treatment, making common infections harder to treat and increasing the risk of complications, prolonged illness and even death.
• “If we use antibiotics carelessly for everything, will they still work when we truly need them?” — This shows why her attitude is dangerous, not merely wrong. Indiscriminate use is exactly what creates resistance.
• “Are all diseases even infections?” — Diabetes, asthma, cancer and heart disease are non-communicable and are today the most common cause of death in India. No antibiotic can touch them; they need lifestyle change and long-term care.
• “So should we stop worrying about diseases, or should we still try to prevent them?” — This brings her to the chapter’s main message: prevention is better than cure.

(i) In which three months were the dengue cases highest?

July, August and September — each with 65 cases, the peak of the year.

(ii) In which month(s) were the cases lowest?

January, with only 10 cases. February is next lowest at 12.

(iii) What natural or environmental factors during the peak months might contribute to the increase?

• The monsoon. July to September is the rainy season in most of India, and the bulletin board itself notes that the arrival of monsoon leads to an increase in malaria and dengue cases.
• Stagnant water collects everywhere — in pots, tyres, coolers, drains, tarpaulins and construction sites. Dengue mosquitos breed in this still water, and the chapter advises avoiding areas with still water.
• Warm, humid weather helps mosquito eggs hatch faster and lets adult mosquitos live longer, so the mosquito population multiplies rapidly.
• Waterlogging and blocked drains create many new breeding sites in towns and cities.
• Cases stay high in October and November because the mosquito population takes time to fall after the rains stop, then decline into the drier, cooler winter.

(iv) Preventive steps the community or government can take before the peak season:

• Launch anti-dengue drives before the monsoon, in May and June, rather than waiting for cases to rise.
• Clear stagnant water from public spaces, empty and scrub coolers weekly, and cover water storage tanks.
• Clean and unblock drains before the rains to prevent waterlogging.
• Carry out fogging and spraying of insecticide in affected localities.
• Distribute or subsidise mosquito nets and repellents, especially in poorer areas.
• Run awareness campaigns through schools, radio and posters teaching people to check their own homes for breeding sites.
• Encourage wearing long-sleeved clothes during peak mosquito hours.
• Prepare hospitals in advance with extra beds, medicines and testing kits for the July–September surge.
• Use biological control such as releasing larvae-eating fish in ponds and water tanks.

Messages to reduce communicable diseases:

• “Wash your hands, wash away disease” — regular handwashing with soap reduces infection by 50%.
• “Cover your cough, protect your class” — always cover the mouth and nose while coughing or sneezing.
• “Sick? Stay home” — resting at home helps you recover and protects everyone else.
• “Don’t share, stay fair to your health” — never share towels, handkerchiefs, water bottles or tiffin.
• “Boil it, cook it, or leave it” — drink boiled or filtered water and eat properly cooked food.
• “No standing water, no dengue” — check the school and home weekly for stagnant water.
• “Vaccines protect you and everyone around you” — complete all recommended vaccinations.
• “A clean campus is a healthy campus” — keep classrooms, toilets and grounds clean.

Messages to reduce non-communicable diseases:

• “Fill half your plate with fruits and vegetables” — eat a balanced diet with whole grains.
• “Less sugar, less oil, more life” — cut down processed, fatty and sugary food and drinks.
• “One hour outdoors, every day” — play, walk, run or cycle instead of sitting.
• “Screens down, health up” — limit screen time, which is linked to obesity, sleep disorders, anxiety and dry eye.
• “Sleep is not lazy — it is repair time” — get enough sleep so body and mind recover.
• “Breathe, stretch, relax” — practise yoga and pranayama to manage stress.
• “Say NO — to tobacco, alcohol and drugs”.
• “Never skip breakfast”.

Messages covering both, and mental health:

• “Prevention is better than cure.”
• “Health is physical, mental AND social” — talk to someone if you feel low or lonely.
• “Antibiotics only on a doctor’s prescription” — and always complete the full course.

How I would run the campaign: weekly assembly talks, student-made posters in corridors, a handwashing demonstration at the washbasins, a doctor’s visit with a question session, a “clean classroom” competition, and a health diary for each student to track food, exercise, sleep and screen time.

There are two reasons, and both matter.

Reason 1 — Antibiotics simply do not work on viruses. Antibiotics work only against bacterial infections because they target parts of bacterial cells that are different from human or other animal cells. Viruses have a completely different structure and do not possess those bacterial parts, so there is nothing for the antibiotic to attack. Colds, coughs and flu are caused by viruses. Taking an antibiotic for them gives no benefit whatsoever — the person recovers because of their own immune system, not the medicine.

Reason 2 — It actively causes harm by breeding antibiotic resistance. This is the more serious reason. When an antibiotic is taken unnecessarily:

• It kills the good bacteria that protect the body from infection.
• The few bacteria that already have resistance survive, and with their competitors gone, they grow and take over.
• These resistant bacteria can transfer resistance to other bacteria, spreading the problem further.
• Resistant bacteria then spread into the community through hospitals, families and even food.

The consequence: the next time that person — or anyone around them — gets a genuine bacterial infection, the antibiotic may no longer work. This makes common infections harder to treat and increases the risk of complications, prolonged illness and even death.

So taking antibiotics for a cold gives you zero help today and real danger tomorrow. Antibiotics should be taken only when prescribed by a doctor, in the correct dose, and for the right duration.

The diseases that may spread are: Hepatitis A, Poliomyelitis and Cholera.

• Hepatitis A — a viral disease of the liver, listed in Table 3.1 under diseases spread through contaminated water and food. Its prevention is drinking boiled water and vaccination.
• Cholera — a bacterial disease of the intestine, also listed under diseases spread through contaminated water and food, causing diarrhoea and dehydration.
• Poliomyelitis — the polio virus is passed out in the excreta of an infected person and spreads through contaminated water. This is exactly why the Odisha sanitation campaign, which reduced open defecation, improved child health.

The diseases that would NOT spread this way:

• Tuberculosis (TB) — spreads through the air, and its site of infection is the lungs. It is contracted by breathing in droplets from an infected person’s cough, not through drinking water.
• Chickenpox — spreads through the air and contact, with the respiratory tract and skin as the sites of infection, not through contaminated water.

The wider lesson: This question shows why safe drinking water and proper sanitation matter so much. A single contaminated water source can spread several serious diseases at once — which is why safe drinking water reduces cases of water-borne diseases, and why building and using toilets improved child health in Bhadrak district.

This happens because the immune system remembers pathogens it has met before.

On first exposure: The pathogen is completely new to the body. The immune system has never encountered it, so it must first recognise the invader and then build the specific defences needed to fight it. This takes time, which is why the response is slow and low, and why we usually fall ill during a first infection.

What happens afterwards: Once the infection is defeated, the immune system retains a memory of that particular pathogen — it keeps a record of what the germ looks like. This is what the chapter calls acquired immunity: protection developed after exposure to a pathogen or a vaccine.

On second exposure: The immune system recognises the pathogen immediately. It does not need to start from the beginning, so the defence is much faster and much stronger. The pathogen is usually destroyed before it can multiply enough to make us ill — which is why we often do not fall sick a second time from diseases like chickenpox or measles.

Why this matters — it is exactly how vaccines work. A vaccine deliberately gives the immune system a safe first exposure, using dead or weakened pathogens, harmless parts of the pathogen, or instructions for our cells to make a harmless part. The immune system is trained to recognise and attack the harmful germ without our ever suffering the disease. Then, if the real pathogen ever arrives, the body responds as though it were a second exposure — fast and strong.

This is precisely why Jenner’s cowpox worked. The two viruses are related, so the immune memory built against cowpox also recognised smallpox.