Health and Diseases Class 9 HPE NCERT

QWhat is the difference between health, disease, and illness in this chapter?

The chapter explains that health, disease, and illness are related but not identical. Health is the overall condition of a person in all aspects of life, including how efficiently the body functions and carries out metabolism (chemical processes that produce energy and materials needed for life). Disease is a biomedically defined deviation from normal body structure or function. Illness is the experience of that deviation—how a person feels and the subjective distress when control systems of the body are not working normally. Being free from disease or illness alone does not fully define health.

QHow does the World Health Organisation (WHO) define health?

According to the chapter, the World Health Organisation (WHO) defines health as “a state of complete physical, mental and social well-being and not merely an absence of disease or infirmity.” This definition is important because it expands health beyond just not being sick. It includes mental well-being (such as coping with stress) and social well-being (how a person functions in family, school, and society). The chapter uses this definition to show why preventing disease is necessary but not sufficient for overall health.

QWhy are disease and illness not the same thing?

The chapter distinguishes the two clearly. A disease is a biomedical condition—meaning doctors can define it as an abnormality in body structure or function compared to normal standards. Illness, on the other hand, is the person’s experience of that condition. Illness includes symptoms and the distress or discomfort a person feels when the body’s control systems are not functioning normally. Because illness is subjective, two people with the same disease may experience illness differently. The chapter also notes that being free from illness or disease does not automatically mean a person is fully healthy.

QWhat are communicable diseases and what causes them?

Communicable diseases are illnesses caused by infectious agents that can spread from one person to another, or from the environment to a person. The chapter states that these infectious agents include bacteria and viruses, and also describes protozoa, fungi, and parasites as causative organisms in the classification of communicable diseases. Because they can be transmitted, communicable diseases often affect many people within a short time (such as common cold). Understanding what causes them and how they spread helps students learn prevention methods like hygiene, sanitation, vaccination, and isolation when necessary.

QHow are communicable diseases classified in this chapter?

The chapter classifies communicable diseases based on their causative organisms. Bacterial diseases include typhoid, cholera, and tuberculosis. Viral diseases include common cold, influenza, HIV infection, and dengue. Protozoal diseases include malaria and kala azar. Fungal diseases include infections of nails, groins, skin, and hair. Parasitic diseases include infestations of intestinal worms such as roundworm, or lice. This classification helps students connect specific examples with the type of microbe involved and understand that prevention and treatment may differ depending on the organism.

QWhat is direct transmission of communicable diseases?

Direct transmission means the disease spreads through immediate contact between a source and a person. The chapter describes several direct routes: (1) direct contact or touching the skin or mucous membrane of an infected person, spreading skin and eye infections; (2) droplet infection, where droplets of saliva or secretions spread illnesses like common cold, tuberculosis, and meningitis; (3) contact with soil, which can transmit agents causing hookworm infestation and tetanus; and (4) inoculation into skin or mucosa, such as rabies through animal bites and hepatitis through contaminated needles.

QWhat is droplet infection and which diseases spread this way?

Droplet infection occurs when droplets of saliva or secretions from a diseased person spread through the air over short distances, especially during coughing or sneezing. The chapter states that droplet infection can spread common cold, tuberculosis, and meningitis. Because droplets can easily reach nearby people, the chapter suggests thinking about why someone with cold, cough, or fever should avoid public places. Preventing droplet spread involves responsible behaviour such as limiting close contact, maintaining hygiene, and keeping infected individuals isolated when necessary to protect others.

QWhat does the chapter mean by indirect transmission and the “5Fs”?

Indirect transmission means germs spread through intermediaries rather than direct contact. The chapter explains this using the “5Fs”: flies, fingers, fomites, food, and fluid. Flies can contaminate food; unclean fingers transfer infection from surfaces to mouth or food; fomites are objects like towels, handkerchiefs, toys, spoons, and glasses that can carry infection; food and fluids (including water and ice) can transmit diseases such as typhoid, diarrhoea, polio, intestinal parasites, and infective hepatitis. Understanding these routes helps students practise hygiene and safe food-water habits.

QWhat are fomites and how can they spread infections?

Fomites are materials or objects that can carry infectious agents. The chapter gives examples such as towels, handkerchiefs, toys, glasses, and spoons used in daily life. If these items are contaminated by an infected person, they can transfer microbes to others who use them. The chapter notes that eye and skin infections and dysentery (diarrhoea with blood) can spread through fomites. A key prevention step mentioned is not sharing personal-use items like towels, soaps, toothbrushes, combs, and razors, as this reduces the chance of transferring microbes through shared objects.

QWho are “carriers” in communicable diseases?

Carriers are healthy people who can spread a disease even if they do not show symptoms. The chapter explains that such individuals may be immune to the organisms they harbour, but they still act as a source of transmission to others. Typhoid is given as an example where carriers can transmit the disease. This idea is important because it shows why community-level prevention is necessary, not only isolating visibly sick individuals. Good hygiene, safe food and water, and awareness can reduce spread even when carriers are present.

QWhat is a vector and which diseases are linked with vectors in the chapter?

A vector is described in the chapter as a living carrier that carries the disease agent on or inside its body and transmits it. Vectors are important in spreading certain communicable diseases. The chapter mentions that vectors can cause diseases like malaria and plague. It also discusses environmental sanitation steps to reduce vector breeding, such as regularly checking areas where water collects and can allow mosquito breeding, and spraying insecticides. Understanding vectors helps students connect environmental cleanliness with disease prevention, especially for mosquito-borne illnesses like malaria.

QWhat personal hygiene steps help prevent communicable diseases?

The chapter lists several personal hygiene measures to reduce exposure to harmful microbes. These include bathing daily and wearing clean clothes, cutting nails, washing hair regularly, brushing teeth twice a day (especially after meals), and keeping ears clean. It also advises not sharing personal items such as towels, soaps, toothbrushes, combs, and razors. Handwashing is emphasized: wash hands before touching food or water, before eating or drinking, before touching the face (eyes, mouth), and before and after using the toilet. These habits reduce transmission of diarrhoea, flu, skin, and eye infections.

QHow do food and water hygiene practices prevent illness?

Food and water hygiene prevents infections that spread through contaminated food, water, and related items. The chapter advises drinking potable water; if water does not appear clean, it should be boiled or filtered before consumption. It recommends eating freshly prepared food or consuming it within four hours of preparation and avoiding fruits and vegetables that are cut and kept open for long periods. Food should be covered to prevent contamination by flies. These steps help prevent diseases mentioned in the chapter such as typhoid, diarrhoea, polio, intestinal parasites, and infective hepatitis.

QWhat is environmental sanitation and why is it important for disease control?

Environmental sanitation means keeping surroundings clean to prevent breeding and spread of disease-causing organisms. The chapter’s measures include using sanitary latrines and avoiding open-air defecation, throwing waste in dustbins to prevent fly breeding, and cleaning drains regularly. It also stresses checking places where water collects to prevent mosquito breeding and using insecticides when needed. Preventing contamination of drinking water is another key step, such as keeping water sources away from garbage disposal areas and storing drinking water containers in clean, safe places. These actions reduce indirect transmission and vector-borne diseases.

QHow do vaccines help in preventing communicable diseases?

Vaccines help by boosting immunity so the body can fight infectious diseases more effectively. The chapter states that many infectious diseases can be prevented by taking vaccines at the appropriate time. Examples listed include diphtheria, pertussis, polio, tetanus, rabies, measles, chickenpox, and typhoid. Vaccination is presented as a preventive tool that works alongside hygiene and sanitation measures. The chapter also encourages students to prepare an immunisation chart and check whether everyone has been vaccinated, and if not, to consult a nearby health centre.

QWhy does the chapter warn against self-medication?

The chapter explains that medicines used to treat infections can kill microbes or slow their growth, and these medicines include anti-virals, anti-fungals, anti-protozoals, and antibiotics. However, it clearly states that such medicines should be taken in the recommended dose and duration as advised by a doctor, and that one should avoid self-medication. The warning is important because incorrect use can lead to poor treatment outcomes and may cause harm. The chapter reinforces this with a note that we must always consult a doctor before taking any medication.

QWhat is isolation and when is it advised?

Isolation is keeping a patient with a communicable disease separated from others in a clean environment to prevent transmission. The chapter recommends isolating patients suffering from diseases that can spread to others. This is particularly useful for infections spread by direct contact or droplets, where close interaction increases risk. Isolation is presented as one part of a broader prevention strategy that includes hygiene, sanitation, vaccination, correct medical treatment, and awareness. By isolating contagious individuals, families and communities can reduce outbreaks and protect vulnerable people.

QWhat are non-communicable diseases and what causes them?

Non-communicable diseases are conditions that do not spread from person to person. The chapter states they may occur due to genetic and lifestyle factors. When caused by unhealthy lifestyle habits, they are called lifestyle diseases. Risk factors include lack of physical exercise, poor dietary habits, inadequate sleep, stress, and habits such as smoking, alcohol use, and tobacco chewing. The chapter classifies non-communicable diseases into lifestyle diseases (diabetes, hypertension, heart diseases, stroke, cancer) and mental health diseases like depression, as well as trauma. Prevention focuses on adopting healthy habits early in life.

QWhat risk factors for hypertension are described in the chapter?

The chapter links hypertension (high blood pressure) to several behavioural factors that can lead to physiological changes and disease outcomes. Dietary risk includes excessive salt intake, especially from packaged and canned foods that contain high sodium. Sedentary lifestyle and lack of exercise can cause excess weight, increasing risk. Mental stress and chronic anxiety also contribute; the chapter advises coping strategies like meditation, yoga, and healthy hobbies. Tobacco use (smoking or chewing nicotine) can lead to hypertension and is also linked with cancers. Managing these risk factors helps reduce chances of hypertension and related complications like heart attacks and strokes.

QHow are obesity, diabetes, and hypertension connected in this chapter?

The chapter highlights a strong link between obesity and certain lifestyle diseases. It states that if a person is obese, there is a high chance of getting diabetes and hypertension. It also notes that hypertension increases the risk of heart attacks and strokes. Diabetes mellitus, if precautions are not taken, can affect many parts of the body, including the brain, eyes, heart, kidneys, blood vessels, muscles, and nerves. The chapter emphasizes prevention through healthy diet, regular exercise, adequate sleep, stress management, and avoiding tobacco and alcohol, starting from childhood to reduce these connected risks.

QWhat is diabetes mellitus according to the chapter and what are common symptoms?

Diabetes mellitus is described as an endocrine disease caused by inadequate secretion of the hormone insulin from the pancreas. Insulin regulates the level of sugar in the body; when insulin is lacking, blood sugar increases, leading to diabetes mellitus. The chapter lists common symptoms as increased hunger, frequent urination, and growing thirst. It also notes that Type 2 diabetes is increasingly reported among children and adolescents, especially those who are obese. Diabetes can be managed mainly through lifestyle changes, physical exercise, and medication to prevent complications in organs like kidneys and eyes.

QWhat lifestyle steps does the chapter suggest to prevent non-communicable diseases?

The chapter emphasizes prevention by adopting healthy habits from childhood and continuing throughout life. It recommends a balanced diet including fruits and vegetables (preferably local and seasonal), wholegrain products including pulses, and milk and milk products. Adequate sleep is advised—6 to 8 hours of sound sleep daily—because poor sleep affects blood pressure, stress levels, and the biological clock. Regular physical activity is recommended for 20–30 minutes daily through sports, walking, climbing stairs, skipping, spot jogging, yoga, or gym workouts. It also stresses mental relaxation through meditation, yoga, and hobbies, and avoiding tobacco, alcohol, and drugs.

QWhat is reproductive health and what problems are discussed in this chapter?

Reproductive health refers to having healthy reproductive organs that perform normal functions. The chapter explains that the reproductive system includes reproductive and genital organs and stresses the need to keep this system healthy. It discusses diseases that adversely affect reproductive health, particularly Reproductive Tract Infections (RTIs) and Sexually Transmitted Infections (STIs). RTIs involve infections of reproductive organs caused by microbes (bacteria, viruses, protozoa) and can result from poor genital hygiene or infected medical instruments. STIs spread through close physical and sexual contact, but some (like HIV and hepatitis B/C) can also spread through non-sexual routes such as needle sharing and infected blood transfusion.

QWhat are the signs and symptoms of RTIs and STIs listed in the chapter?

The chapter lists common signs and symptoms of RTIs and STIs that students and parents should recognize. These include itching or a burning sensation in the genital organs, foul-smelling discharge from the vagina or penis, blisters, sores, or swelling on or near the genitals, anus, or its mouth, and pain or burning sensation with increased frequency of urination. The chapter notes that one may have one or more of these symptoms. If such signs appear, it advises seeking treatment from a qualified doctor and not feeling shy about discussing the issue, because complete and proper treatment is important.

QHow can RTIs and STIs be prevented and controlled according to the chapter?

Prevention and control of RTIs and STIs focus on hygiene, responsible behaviour, and proper medical care. The chapter advises maintaining proper genital hygiene to prevent RTIs, including daily bathing and cleaning the genital area with soap and water. It notes that girls and women need extra menstrual hygiene precautions because infection risk can increase during menstruation. It also advises staying away from casual sexual relationships and practising responsible sexual behaviour; if sexual relations cannot be avoided, a condom must be used. For treatment, the chapter emphasizes consulting a qualified doctor (not quacks), completing treatment, and treating both partners properly in RTI/STI cases.

QWhat menstrual hygiene steps are recommended for girls and women?

The chapter provides clear steps to maintain menstrual hygiene and prevent infections. It recommends using clean homemade cloth pads or disposable pads/napkins during menstruation. Sanitary pads should be changed at frequent intervals, at least twice a day. If homemade cloth napkins are reused, they must be washed daily with soap and water and dried in a sunny and dry place to prevent infection. The chapter also notes that during menstruation there are more chances of infection because of blood flow, so careful hygiene—daily bath and cleaning the genital area properly—is especially important during this time.

QWhat is HIV, and how does it relate to AIDS as explained in the chapter?

HIV stands for Human Immunodeficiency Virus. The chapter explains that HIV is found only in human beings and attacks the immune system, particularly by entering white blood cells that normally fight germs. When HIV remains in the body for a long time, it destroys immune defence, and then many diseases such as tuberculosis, fungal infections, and cancer begin affecting the body. At that stage, the person is said to have AIDS (Acquired Immune Deficiency Syndrome). The chapter clarifies that having TB or cancer does not automatically mean a person has HIV/AIDS. It also explains the terms: acquired (not inherited), immune deficiency (weak defence), and syndrome (a group of diseases).

QHow is HIV transmitted and what myths are corrected in the chapter?

The chapter states that HIV can enter the body through unsafe sexual intercourse without a condom with an infected partner, use of unsterilised needles or syringes, transfusion of HIV-infected blood, and from an infected mother to her child before, during, or after birth. It identifies unsafe sexual contact as the most common route. It also corrects major myths: HIV does not spread through air, water, or food, and it does not spread through mosquito or animal bites because the virus does not survive or reproduce outside the human body, and mosquitoes do not inject previously sucked blood. The chapter highlights that myths cause discrimination and should be removed through awareness.

QHow is HIV detected and what is the “window period” mentioned in the chapter?

The chapter explains that HIV infection can only be diagnosed by a specific blood test conducted at Integrated Counselling and Testing Centres in government-run hospitals, which maintain privacy and confidentiality. The test detects antibodies produced by the body against HIV. However, these antibodies appear only after about six weeks to six months after acquiring the infection. This time gap is called the “window period.” If a test is done during the window period, it may show a negative result even if infection has occurred. Therefore, the chapter advises waiting until the window period is over to get accurate testing.

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