Solutions-NCERT-Class-8-Science-Curiosity-Chapter-3-Health: The Ultimate Treasure-CBSE

• The common cold is caused by viruses.
• The body responds to a common cold (caused by viruses) through the immune system.
• Symptoms (runny nose, sore throat, cough) appear as the body fights the infection.
• The immune system makes antibodies to destroy the virus.
• White blood cells attack infected cells.
• Recovery is supported by rest, drinking fluids, and medicines for relief (like fever reducers).

• Smallpox and polio have almost disappeared because of mass vaccination programs (like Edward Jenner’s smallpox vaccine and polio vaccines).
• On the other hand, non-communicable diseases (NCDs) such as diabetes and heart disease are rising. This is mainly due to modern lifestyles—unhealthy eating habits (junk and processed foods like pizza and burgers), lack of physical activity, stress, and people living longer.

Yes, climate change can increase existing diseases and even introduce new ones by altering temperature, rainfall, and ecosystems.

• Rising Temperatures: Warmer climates help mosquitoes and other vectors survive in new regions → spread of diseases like malaria, dengue, chikungunya.
• Extreme Weather: Floods, cyclones, and heavy rains contaminate water → more waterborne diseases (cholera, diarrhoea, typhoid).
• Changing Ecosystems: Animals, insects, and microbes shift to new habitats, carrying unfamiliar pathogens → risk of new infectious diseases.
• Food & Water Insecurity: Heat and drought affect crops → malnutrition and weakened immunity.
• Air Pollution: Worsens respiratory illnesses like asthma and lung infections.

Effect of Stress and Worry on Health

• Hormonal changes: Stress increases hormones like cortisol and adrenaline, which disturb normal body functions.
• Weak immune system: Body’s defense lowers → more prone to infections (cold, flu).
• Digestive problems: Can cause stomach pain, acidity, or loss of appetite.
• Heart problems: Long-term stress raises blood pressure and risk of heart disease.
• Sleep issues: Worry makes it hard to sleep → tiredness and poor concentration.
• Mental health: Leads to anxiety, depression, and mood swings.

• Weaker Immunity – Infants, elderly, and sick people have lower resistance to infections.
• Poor Nutrition – Malnourished people are more vulnerable to diseases.
• Living Conditions – Crowded areas, poor sanitation, and unsafe water increase spread.
• Economic Factors – Poor communities may lack access to healthcare and medicines.
• Pre-existing Illnesses – People with diabetes, heart disease, or lung problems are at higher risk.
• Occupational Exposure – Health workers, farmers, or people in contact with animals may face higher exposure.

Vulnerability depends on immunity, nutrition, living conditions, economic status, and health background.

(b) (ii) and (iii)

(i) Immediate actions by the school

• Ask sick students to stay home and rest.
• Inform parents about the flu outbreak.
• Ensure classrooms are well-ventilated.
• Arrange regular cleaning of benches, doorknobs, and shared items.
• Encourage students to wash hands frequently and wear masks if needed.

(ii) Responding to a sick classmate kindly

• Politely suggest they should inform the teacher and rest at home.
• Offer them tissues or remind them gently to cover mouth/nose while coughing or sneezing.
• Show care and concern instead of blaming or avoiding them rudely.

(iii) Protecting yourself and others

• Wash hands often with soap and water.
• Avoid touching face, eyes, and nose unnecessarily.
• Keep safe distance from sick classmates.
• Use a mask in crowded areas.
• Eat healthy food and get enough sleep to boost immunity.

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

• Before: Consult a doctor, take preventive medicines if prescribed, pack mosquito nets/repellents.
• During: Wear long-sleeved clothes, sleep under mosquito nets, use repellents, avoid stagnant water near stay.
• After: Watch for fever, chills, or other malaria symptoms and seek medical help quickly.

(ii) Explaining importance to sibling

• Mosquitoes spread malaria; nets and repellents keep them away.
• Using them protects the whole family, especially children, from falling sick.
• Prevention is easier and safer than treatment.

(iii) If travellers ignore health advisories

• High risk of getting malaria.
• May suffer serious illness, hospitalisation, or even death.
• Infected travellers can also spread the disease to new areas.

(i) What to say to uncle

• Politely explain that smoking harms lungs, heart, and can cause cancer.
• Remind him that real friends won’t force harmful habits.
• Suggest healthier ways to relax and socialize.

(ii) If a friend offers a cigarette

• Refuse firmly but politely: “No thanks, I don’t smoke.”
• Change the topic or walk away without hurting their feelings.
• Set an example by making a healthy choice.

(iii) How schools can help

• Organize awareness programs on dangers of smoking, alcohol, and drugs.
• Encourage sports, hobbies, and stress-relief activities.
• Invite doctors or experts to talk to students.
• Provide counselling and peer-support groups.

Here’s how Vinita can question Saniya to make her think and correct her misunderstanding:

• Do antibiotics work against viruses like cold, flu, or COVID-19?”
• “What happens if people take antibiotics for viral infections—doesn’t that cause antibiotic resistance?”
• “Have you heard that antibiotics only kill bacteria, not viruses?”
• “Why do doctors sometimes say rest and fluids are enough instead of giving antibiotics?”

Vinita can ask questions that highlight the difference between bacterial infections (where antibiotics work) and viral infections (where they don’t), and also the danger of antibiotic resistance.

(i) The dengue cases were highest in July, August, and September.

(ii) The cases were lowest in January.

(iii) Natural or environmental factors during the peak months, such as the rainy season and standing water for mosquito breeding, might contribute to the increase in dengue cases.

(iv) The community or government can take preventive steps like removing stagnant water, using mosquito nets, and spraying insecticides during this period regularly to reduce the spread of dengue.

Key Messages for a School Health Campaign

To reduce Communicable Diseases:

• Wash hands regularly with soap and water.
• Cover mouth and nose when coughing or sneezing.
• Get vaccinated on time.
• Keep surroundings clean and prevent mosquito breeding.
• Stay home when sick to avoid spreading illness.

To reduce Non-Communicable Diseases (NCDs):

• Eat a balanced diet: more fruits and vegetables, less junk food.
• Exercise or play outdoors daily.
• Limit screen time and get enough sleep.
• Avoid tobacco, alcohol, and harmful substances.
• Manage stress through yoga, hobbies, or relaxation.

Why Antibiotics Should Not Be Taken for Viral Infections : 

• Antibiotics don’t work on viral infections, and their misuse can cause resistance and other health problems.
• Antibiotics only kill bacteria, not viruses.
• Common cold, cough, and flu are caused by viruses, so antibiotics have no effect.
• Taking antibiotics unnecessarily can kill useful bacteria in the body.
• Misuse of antibiotics leads to antibiotic resistance → harmful bacteria stop responding to medicines, making future infections harder to treat.

The diseases that may spread if drinking water gets contaminated by the excreta from an infected person are Hepatitis A, Poliomyelitis, and Cholera.