NCERT Solutions Curiosity Chapter 3 Chapter opener — Probe and ponder

The body fights back through its immune system, and almost everything we call “having a cold” is that fight, not the virus itself.

Step by step, this is what happens:

1. The virus enters through the nose or mouth and settles in the lining of the respiratory tract.
2. The immune system recognises it as foreign and rushes blood and defence cells to the nose and throat. The lining swells and makes extra mucus — this is the nasal congestion and discharge and the sore throat listed in Table 3.1.
3. Sneezing and coughing throw the virus and the mucus out of the body. They are protective actions, which is exactly why they also pass the infection on to others.
4. The body may raise its temperature. A mild fever makes conditions less comfortable for the pathogen and makes the immune response work faster.
5. Body ache and tiredness follow because energy is being spent on the defence rather than on ordinary work.

In most people the cold clears in a few days. Afterwards the immune system remembers that particular virus, so the same one troubles us less next time.

Because the two groups of diseases have completely different causes, and only one of them can be stopped by a vaccine.

Once enough people were vaccinated, the smallpox and polio viruses could not find new bodies to move into, and they died out. Diabetes and heart disease work differently. The chapter names the reasons for their rise in India: more processed food, less physical activity, and longer lives. None of these is a germ, so no injection can protect against them.

This is why the chapter says that today most deaths in India are caused by non-communicable diseases, even though a century ago infections were the biggest killers.

Yes — and more certainly, it changes where and when existing diseases strike, which is already visible in India.

• Vector-borne diseases spread to new places. Mosquitos breed in warm, wet conditions. The notice board on page 28 states that the arrival of the monsoon leads to an increase in malaria and dengue cases. If warm, wet weather lasts longer in the year, or reaches hill areas that were previously too cold, mosquitos survive there too — and malaria and dengue arrive with them.
• Floods and drought spoil drinking water. Flood water carries excreta into wells and pipes. That is the route for cholera, typhoid and hepatitis A, all listed in Table 3.1.
• Pathogens meet new populations. When people and animals are forced to move because of drought, floods or changing farmland, a pathogen that lived quietly in one animal population can reach humans who have never been exposed to it — and who therefore have no immunity to it.
• Heat and air pollution add to the load. The board calls air pollution a public health emergency and one of the leading risk factors for health; it worsens asthma and other breathing problems.

They act on the body, not only on the mind — which is exactly why the WHO definition of health includes mental and social well-being alongside physical well-being.

Long-lasting stress or worry usually shows itself in this order:

1. Sleep is disturbed first. A worried mind stays alert at night, so the body does not get the rest in which it repairs itself.
2. Eating changes. Some people lose their appetite and lose weight; others eat much more than usual. Either way the body stops getting a balanced diet.
3. Physical symptoms appear — headaches, stomach upset, tiredness, difficulty in concentrating. These are real, not imagined.
4. Resistance to infection falls. Poor sleep and poor nutrition weaken the immune system, so infections that the body would normally shrug off now take hold.

Activity 3.1 is exactly this story: the boy had no infection at all, yet he had headaches, lost weight and could not sleep. His illness began with loneliness.

Because the pathogen may be the same for everybody, but exposure and the ability to resist are not.

• Environment differs. Where housing is crowded, an airborne disease passes on much faster. Where there is no toilet or no safe drinking water, cholera, typhoid and hepatitis A spread easily — this is precisely why the Bhadrak sanitation campaign in Activity 3.6 cut down diarrhoea and infections. Where water is left standing and rubbish is not cleared, as in Fig. 3.3b, mosquitos and houseflies breed and carry disease.
• Immunity differs. Very young children, elderly people, and those already living with a chronic disease such as diabetes have weaker defences, so the same infection hits them harder.
• Nutrition differs. A body that is not getting a balanced diet cannot maintain a strong immune system.
• Access to prevention and care differs. Groups who have received their vaccines, who can reach a doctor early, and who can afford to stay at home and rest recover better than those who cannot.

Frame questions of your own about health, and then find the answers from the chapter, from a trusted health website, or from a doctor or health worker. Good questions begin with why, how, when and what if.

Sample questions:

• If a vaccine cannot cure a disease, why is it given to a healthy person?
• Why does the same cold virus make one member of the family ill and leave another untouched?
• Why do doctors insist that the full course of an antibiotic be finished even after the fever has gone?
• Diabetes is not caused by a germ — so why is it becoming more common in children?
• How does an insect that bites me give me a disease it never suffers from itself?
• Can loneliness really be called a health problem?
• How is the Air Quality Index measured, and what does today's reading in my town mean for me?