Health and Hygiene | ICSE Class 8 Biology Notes

This note covers health and hygiene, communicable diseases, their causes and spread, vectors, disease prevention, immunity, vaccination and immunisation, harmful effects of tobacco, alcohol and habit-forming drugs, and first aid for common injuries and emergencies.

What do health, hygiene and disease mean?

Definition: Health is a state of complete physical, mental and social well-being, rather than merely being free from disease. Hygiene means practices that help maintain health and prevent disease.

Physical well-being concerns the body, mental well-being concerns thoughts and feelings, and social well-being concerns relationships with other people. A healthy person can generally perform tasks more efficiently and cope well with different and difficult situations.

A disease is a condition that affects the normal working of the body or mind. Good health therefore involves more than checking whether a person has a fever. Rest, feelings, relationships, food, physical activity and surroundings also matter.

How are signs different from symptoms?

A symptom is something a person feels, such as pain, tiredness or dizziness. A sign is something that can be observed or measured, such as a rash, swelling or a raised body temperature. These help doctors understand an illness.

A pathogen is a disease-causing agent. Communicable diseases are caused by pathogens and can spread from one person to another. Non-communicable diseases, such as diabetes, a disease involving raised blood sugar, do not spread from person to person. Different diseases therefore require different preventive measures.

Nutritious food, regular exercise, adequate sleep and time with friends and family support health. Maintaining personal cleanliness and clean surroundings is also important. These habits support well-being, while specific preventive measures help protect against particular diseases.

Three overlapping coloured circles are labelled Mental, Physical and Social. They contain symbols of a head, a running person and a group of people respectively, linking the three aspects of health.

See Fig. 3.1 in your NCERT textbook

How do communicable diseases spread?

Transmission means the passing of a pathogen from one person or source to another person. Infection occurs when a pathogen enters and establishes itself in the body. The route of transmission helps explain which preventive action is useful. Respiratory means relating to breathing and the organs and passages involved in it.

Some diseases spread through air when an infected person coughs or sneezes. Others spread through food or water containing pathogens. Contaminated means containing harmful or unwanted material; here, it refers to material carrying disease-causing agents.

Some pathogens pass through direct contact or indirectly through shared personal items. A vector is a living carrier that transmits a pathogen. Mosquitoes and houseflies can act as vectors. The carrier and the disease-causing agent are different parts of transmission.

Which diseases should be compared?

The following table brings together the causes, main signs and symptoms, and prevention of the six diseases. Influenza is also called flu. A virus is an infectious agent that multiplies inside living cells. Transmission through air means that infectious material is carried through the air to another person. Protozoa are single-celled organisms; some cause disease.

The immune system is the body's system of cells, tissues and organs that helps defend it against disease. HIV stands for human immunodeficiency virus, which damages this system. AIDS, acquired immunodeficiency syndrome, is the advanced condition of severe immune damage associated with HIV infection. A syndrome is a group of associated signs and symptoms.

Nasal congestion and discharge means a blocked and running nose. Isolation means keeping an infectious patient apart to reduce transmission. Profuse sweating means sweating heavily; periodic chills are repeated episodes of feeling cold and shivering.

Nausea means feeling that one may vomit; diarrhoea means passing loose or watery stools frequently. A repellent discourages insects from approaching or biting. Sterile means free from living microorganisms or microbes, organisms too small to see clearly without magnification. Blood screening means testing donated blood for infections before use.

A parasite lives in or on another organism, called its host, and obtains nourishment from it. Vaccination means giving a vaccine, a preparation that trains the immune system against a particular pathogen.

An infected person is drawn on the left and a healthy person on the right. Arrows link them through direct contact, air, indirect contact, food and mosquitoes or insects. A rabid animal is drawn below.

See Fig. 3.4 in your NCERT textbook

The figure groups several possible routes; it does not mean that every disease spreads by every route. A rabid animal is an animal infected with rabies, a viral disease. Flu prevention and mosquito control act on different routes.

How do vectors spread malaria, dengue and chikungunya?

The malaria parasite is Plasmodium. The female Anopheles mosquito transmits it; the mosquito itself is not the pathogen that causes malaria.

Dengue and chikungunya are viral diseases transmitted by Aedes mosquitoes. They are therefore vector-borne diseases, meaning diseases whose pathogens are carried by vectors. Sharing this route does not mean they have the same causative agent.

What is the basic malaria transmission sequence?

1. An infected female Anopheles mosquito bites a human and introduces the malaria parasite into the body.
2. The parasite first multiplies in liver cells, then attacks red blood cells, the blood cells that transport oxygen.
3. An Anopheles mosquito feeding on an infected person takes up parasites with the blood.
4. The parasites develop in the mosquito, and an infected mosquito can introduce them into another human during a later bite.

This sequence explains why preventing bites and controlling mosquito breeding are useful together. The malaria parasite needs both human and mosquito hosts to complete its life cycle. A life cycle is the sequence of stages in an organism's development and reproduction.

How can the transmission route be interrupted?

Avoid allowing water to stagnate, meaning remain still, around homes. Clean household coolers regularly and prevent collections of standing water. Mosquito nets, long-sleeved clothing, repellents and wire mesh on windows and doors help reduce contact with mosquitoes.

Vector control means reducing the vectors or their breeding places. It protects the community as well as individuals. Cleaning breeding sites tackles the supply of mosquitoes, while nets and other barriers help prevent bites from mosquitoes already present.

Note: Malaria is caused by a protozoan parasite, whereas dengue and chikungunya are caused by viruses. Write the pathogen separately from the mosquito vector when comparing these diseases.

What makes HIV infection different from ordinary social contact?

HIV damages the immune system. In particular, it reduces the number of a type of white blood cell that helps coordinate the body's response to infection.

As these cells decline, the person becomes less able to fight infections that the body could otherwise overcome. Bouts of fever, diarrhoea and weight loss can occur. HIV infection and the appearance of AIDS are separated by a time interval that may vary considerably.

Which routes transmit HIV?

Transmission generally occurs through sexual contact with an infected person, transfusion of infected blood or blood products, sharing contaminated needles, or transmission from an infected mother to her child. Transfusion means transferring donated blood or blood components into a person's bloodstream.

The relevant issue is exposure to infected body fluids through these routes. Mere touch or ordinary physical contact does not spread HIV. A person living with HIV therefore needs support and medical care, rather than exclusion from family and social life.

How can transmission be prevented?

Blood used for transfusion should be screened. Needles and syringes should be sterile and should not be shared. Safer sexual practices, including the use of condoms, reduce sexual transmission. A condom is a protective barrier used during sexual contact.

Medical advice, testing and appropriate care are important for people at risk of infection. The preventive action must match the route: safe injection equipment tackles exposure through needles, while screening donated blood tackles exposure through transfusion. Avoiding a handshake does neither.

Compassion and accurate information belong together. HIV is an infectious agent, but its presence does not make every interaction infectious. Understanding the actual routes helps people take effective precautions without treating affected people unfairly.

How does the immune system protect the body?

Immunity is the body's ability to fight disease-causing agents. Exposure to pathogens does not necessarily lead to disease because the body has defences. These include barriers that limit entry and responses that act against pathogens entering the body.

What are the body's first defences?

Innate immunity is the non-specific defence present from birth. Non-specific means that it does not depend on recognising just one particular pathogen. Skin forms a physical barrier. Mucus, the sticky lining secretion in breathing passages, helps trap microbes.

The respiratory tract is the system of passages through which air moves during breathing. Tears, saliva and stomach acid also help prevent microbial growth. Certain white blood cells, which are blood cells involved in defence, can engulf and destroy microbes.

Why does previous exposure matter?

Acquired immunity develops after exposure to a pathogen or vaccine and is specific to the pathogen. It is characterised by memory, the retained ability to respond more effectively after an earlier encounter. Antibodies are protective proteins produced by certain immune cells in response to substances recognised by the immune system.

1. The body encounters a particular pathogen for the first time.
2. It produces a first immune response, which is of low intensity compared with the response to a later encounter with that same pathogen.
3. The immune system develops memory of the encounter.
4. A subsequent encounter with the same pathogen produces a more rapid and much stronger response.

This memory helps explain the action of vaccines. The important condition is exposure to the same pathogen: recognising one disease-causing agent does not mean the body has learned to recognise all others. General hygiene and specific protection therefore have different roles.

Draw four labelled boxes: first encounter with a pathogen; first immune response; immune memory; stronger response on encountering the same pathogen again. Connect the boxes with arrows showing the sequence, rather than the movement of a substance.

How do vaccination and immunisation differ?

A vaccine is a preparation that trains the immune system to recognise a particular pathogen. Vaccination means giving a vaccine. Immunisation is the process of developing protection against a disease, commonly through vaccination. The action and the development of protection are related but distinct.

Vaccines may use weakened or dead pathogens, or harmless parts of pathogens. Some newer vaccines instruct body cells to make a harmless part that the immune system learns to recognise. Vaccines therefore need not contain a whole living disease-causing organism.

What happens after vaccination?

The immune system responds to the vaccine material and develops memory. If the corresponding pathogen is encountered later, it can be recognised more quickly. Immune memory is the retained ability to respond more effectively after an earlier encounter.

Vaccines are preventive rather than curative: they help minimise serious disease before it occurs and do not treat an illness already established. Vaccination and treatment therefore serve different purposes. Examples of diseases against which vaccines are used include measles, polio and tetanus.

What is the difference between active and passive protection?

Active immunity develops when the person's own body produces antibodies after exposure to vaccine material or a pathogen. It takes time to develop its full response. Vaccination is a way to stimulate this active response without undergoing the corresponding disease.

Passive immunity is protection obtained through ready-made antibodies. Antibodies passed from mother to baby are an example. Doctors can also give prepared antibodies when rapid protection is needed. This shows why immunisation is a broader idea than simply administering a vaccine.

A useful distinction is to ask what is being supplied: a vaccine stimulates the body's response, whereas passive protection supplies antibodies already made. Neither replaces hygiene. Preventing exposure, supporting general health and developing specific immunity contribute in different ways.

How do personal and public hygiene prevent disease?

Personal hygiene means practices that keep one's body and personal belongings clean. Public hygiene concerns cleanliness and health protection in shared surroundings. Sanitation includes safe disposal of waste and human excreta, which are body wastes such as faeces and urine.

Handwashing with soap and water removes pathogens. Covering the mouth and nose while coughing or sneezing helps limit their spread. Avoiding shared towels and handkerchiefs reduces indirect contact with contaminated personal items. Staying at home when unwell helps minimise spread to others.

Which measure acts on which problem?

Susceptibility means being open to infection or disease. Each measure below addresses a different part of disease prevention.

The table shows why a single measure is not enough for every route. Clean drinking water matters for water-borne infections, while mosquito control targets vector-borne infections. Both belong within community health work.

Why is prevention a shared responsibility?

Personal habits and shared services work together. An individual can wash hands and avoid sharing personal items. Communities also need clean water, waste disposal and control of mosquito breeding. Keeping surroundings clean helps support the health of many people using the same spaces.

When illness occurs, medical assessment is still important. Antibiotics are medicines used against infections caused by bacteria, single-celled microorganisms; they do not treat viral infections such as influenza. Their use should follow a doctor's prescription, correct dose and duration rather than guesswork.

Why are tobacco, alcohol and habit-forming drugs harmful?

Substance misuse means harmful use of substances such as alcohol or habit-forming drugs. Addiction involves attachment to their effects and repeated use despite harm. A temporary feeling of well-being does not show that a substance is safe.

What damage can tobacco cause?

Tobacco contains nicotine, an addictive chemical that raises heart rate and blood pressure. Cancer involves uncontrolled cell division. Smoking is associated with increased occurrence of lung and throat cancers and heart disease. Chewing tobacco is associated with increased risk of cancer of the mouth.

Smoking also increases carbon monoxide, a poisonous gas, in the blood. This reduces the oxygen carried by the blood and causes oxygen deficiency in the body. Tobacco is therefore harmful when smoked and when chewed, although the routes of exposure differ.

How do alcohol and drugs affect health?

Long-term misuse of alcohol and drugs damages the nervous system, the body's signalling and control system, and liver. Excessive drug doses may cause loss of consciousness, meaning loss of awareness and responsiveness, failure of breathing or death. Sharing contaminated injection needles can also transmit infections such as HIV, adding an infection risk to the drug's direct effects.

Dependence means that stopping a regularly used substance can cause an unpleasant withdrawal reaction. Withdrawal symptoms can include anxiety, shakiness, nausea and sweating. In some cases they can be severe and even life-threatening, so medical supervision may be needed.

Tolerance means that repeated use reduces the response to a given amount, encouraging use of larger amounts. Addiction, tolerance and dependence are connected, but they describe different features of substance use. Experimenting even once can be a forerunner to addiction.

How can harmful use be prevented?

Resist pressure to try these substances. Discuss stress and difficult feelings with trusted adults, and seek counselling or professional help when needed. Sports, reading, music and other constructive activities provide healthier ways to spend time and cope with pressure.

A person experiencing substance dependence needs support and treatment. Effects can extend to schoolwork, friendships and family well-being. Recognising a problem early and seeking appropriate help are more useful than hiding it or assuming that stopping will always be easy.

What is first aid, and what should a first-aid box contain?

First aid is the initial assistance given for an injury or sudden illness before professional medical care is available. Its aims are to preserve life, prevent the condition from worsening and promote recovery. A casualty is the injured or suddenly ill person.

A first aider is a person trained to give this initial assistance. First aid has limits and does not replace professional treatment. Practical techniques should be learned through supervised demonstrations, so that the helper knows how to use available materials safely.

What principles guide the first response?

1. Check that the surroundings are safe for both the casualty and the helper before approaching.
2. Find out what has happened and check the person's condition without unnecessary movement.
3. Call for a trained adult and arrange professional medical assistance appropriate to the emergency.
4. Reassure the person and provide only the care for which the helper has been trained while help is arriving.

Safety matters because a helper who enters danger can become another casualty. Calm reassurance helps gain the person's confidence. Avoid unnecessary crowds around the casualty. There may be more than one injury, so care should not focus on just the most obvious one.

Which materials help?

A first-aid box should be accessible at home and school. Useful items include disposable gloves, sterile dressings, bandages, adhesive tape, a triangular bandage and splinting material. A dressing covers a wound, while a bandage supports or secures a dressing or injured part.

A splint is a support used to limit movement of an injured body part. Supplies should be inspected regularly, used items replaced and expired items discarded. Merely having equipment is not enough; the person using it must understand its correct purpose.

What first aid is useful for burns, bleeding and fractures?

A burn is tissue damage caused by heat or another damaging agent. Bleeding is loss of blood from damaged blood vessels. A fracture is a crack or break in a bone. These injuries require different immediate actions.

How should a burn be handled?

Move away from the source of burning when this can be done safely. Cool a heat burn with cool running water, and arrange appropriate medical help. Cover it loosely with a clean, non-fluffy covering after cooling. Do not burst blisters or apply oils or household pastes, which can contaminate the injured area. Cooling with water removes heat and limits damage to deeper tissues.

Do not pull away clothing stuck to a burn. A large, deep or otherwise serious burn needs urgent professional care. The purpose of first aid is to limit further damage and protect the injured area, rather than to try to complete treatment at home.

How should external bleeding be managed?

External bleeding is blood loss visible outside the body. For an ordinary bleeding wound with no embedded object, a trained helper can use the following sequence. An embedded object is an object lodged in the wound.

1. Call for help and use disposable gloves, if available, to reduce direct contact with blood.
2. Place a clean dressing or cloth over the wound.
3. Apply firm, direct pressure through the covering to help control the bleeding.
4. Arrange urgent medical care if bleeding is heavy or does not stop, while continuing appropriate pressure.

Do not pull out a deeply embedded object or press directly on it. Such a wound needs professional care. A wound covering helps protect the injury, but serious blood loss requires urgent medical assistance rather than waiting for a dressing alone to solve the problem.

What should be done for a suspected fracture?

Keep the injured part still and supported in the position found. A trained first aider may use a suitable splint or sling; a sling supports an injured arm. Do not straighten the limb or push a protruding bone back into place, because movement can injure the surrounding tissues further. Obtain medical help.

What should be done for an object in the eye or unconsciousness?

A foreign body in the eye is material that does not belong there, such as a dust particle. The eye is delicate, so rubbing or attempting to pick out material can make an injury worse. Obtain help from a trained adult.

How can the eye be protected?

Do not rub the affected eye. A loose surface particle may be rinsed away gently with clean water. If the object is embedded, do not try to remove it. Persistent pain, continued irritation or an embedded object requires prompt medical attention.

There is a difference between a loose particle and something stuck into the eye. Simple rinsing applies to loose surface material. Do not probe the eye with fingers or an instrument. The aim is to avoid further damage while arranging appropriate care.

Why is unconsciousness an emergency?

Unconsciousness means loss of awareness and responsiveness. Call for emergency medical help and a trained first aider. Check whether the person responds and is breathing normally. Do not give food, drink or medicine by mouth to an unconscious person.

If the person is breathing normally, a trained helper should protect the airway and monitor breathing. The airway is the passage through which air reaches the lungs. Follow emergency-service instructions about positioning, especially when a fall or other injury may have occurred.

If the person is unresponsive and not breathing normally, call emergency services immediately and follow their instructions to begin cardiopulmonary resuscitation, abbreviated CPR, without delay. CPR is an emergency procedure used to maintain circulation when the heart has stopped. Its techniques should be learned through practical training.

First aid for unconsciousness begins with recognising the emergency and obtaining help. Do not give anything by mouth. If the person is breathing normally, protect the airway and continue monitoring breathing while help arrives; if normal breathing stops, follow emergency guidance and begin CPR promptly.

What first aid is needed for swallowed poison, snake bites and stings?

A poison is a substance that can harm the body when it enters it in a harmful amount. Venom is a poisonous substance delivered by an animal through a bite or sting. These emergencies need prompt action and appropriate medical advice.

What should be done after swallowing poison?

Call for urgent medical help. Do not make the person vomit, because vomit can enter the lungs and a swallowed corrosive substance can injure the food pipe again. Do not give a household remedy. Do not give anything by mouth unless a medical professional instructs this. Keep the product container or label to show the medical team, if it is safely available.

Tell the medical team what is known about the substance and the incident. An unconscious person must not be given anything by mouth. Prevention includes keeping cleaning liquids and other dangerous chemicals secured in their original containers, away from children.

What should be done after a snake bite?

Treat a suspected snake bite as an emergency. Call for medical help immediately, reassure the person and keep them still. Immobilise means prevent movement; a trained helper should immobilise the bitten limb and arrange urgent transport for medical care.

Do not cut or suck the wound, tie a tight band around the limb, or try to catch the snake. Antivenom is a medical preparation containing antibodies against venom. Doctors decide on antivenom and other treatment; it is not a home first-aid remedy.

How should an insect sting be handled?

Move away from the insect and seek a trained adult's help. If a sting remains in the skin, a trained helper can remove it promptly. Wash the area and use a cold pack wrapped in cloth to reduce local discomfort and swelling.

Breathing difficulty or swelling of the mouth or throat after a sting requires emergency medical help. Such symptoms may indicate a severe allergic reaction, an excessive immune response to a substance. Do not treat these signs as merely an ordinary painful sting.

Glossary

• Health — A state of physical, mental and social well-being, rather than simply the absence of disease.
• Hygiene — Practices that help maintain health and prevent disease through cleanliness and related protective habits.
• Pathogen — A disease-causing agent that can enter the body and produce infection.
• Communicable disease — A disease caused by a pathogen that can spread from one person to another.
• Vector — A living carrier that transmits a pathogen between hosts, as a mosquito does in malaria.
• Symptom — A change felt by an unwell person, such as pain, tiredness or dizziness.
• Immunity — The body's ability to defend itself against disease-causing agents through its immune system.
• Antibody — A protective protein produced by certain immune cells in response to material recognised by the immune system.
• Vaccination — The administration of a vaccine to stimulate an immune response against a particular pathogen.
• Immunisation — The process of developing protection against a disease, commonly through the administration of a vaccine.
• Addiction — Attachment to the effects of a substance that encourages repeated use despite harmful consequences.
• Dependence — A condition in which stopping regular substance use can produce an unpleasant withdrawal reaction.
• First aid — Initial assistance for an injury or sudden illness before professional medical treatment is available.
• Fracture — A crack or break in a bone requiring support, restricted movement and medical assessment.
• Antivenom — A medical preparation containing antibodies against venom, administered under professional care when considered necessary.

Common errors and misconceptions

• Misconception: Health means only having no disease. Correct: Physical, mental and social well-being all belong to health; relationships and feelings matter alongside the condition of the body.
• Misconception: A mosquito is the organism that causes malaria. Correct: Plasmodium causes malaria. An infected female Anopheles mosquito is the vector that transmits the parasite to humans.
• Misconception: Malaria, dengue and chikungunya have the same pathogen. Correct: Malaria is caused by a protozoan parasite, while dengue and chikungunya are viral diseases transmitted by Aedes mosquitoes.
• Misconception: Touching someone with HIV spreads infection. Correct: HIV does not spread through mere touch. Its transmission involves particular routes, such as infected blood or contaminated injection equipment.
• Misconception: Vaccination and immunisation describe exactly the same action. Correct: Vaccination is giving a vaccine; immunisation is developing protection. Ready-made antibodies can also provide passive protection.
• Misconception: Antibiotics cure influenza because it is an infection. Correct: Influenza is viral. Antibiotics act against bacterial infections and should be used according to medical advice.
• Misconception: A person can easily stop any habit-forming substance without help. Correct: Dependence can cause withdrawal symptoms, which in some cases are severe and require medical supervision.
• Misconception: Making a person vomit is the first response to swallowed poison. Correct: Obtain urgent medical advice and do not induce vomiting or give household remedies.

Exam-style questions with model answers

Q1. Health includes physical, mental and social well-being. Hygiene consists of practices that maintain health and help prevent disease. Using these descriptions, distinguish health from hygiene in two points. [2 marks]

1. Health describes a person's state of physical, mental and social well-being.
2. Hygiene describes the practices used to maintain health and help prevent disease.

Q2. Malaria is caused by the protozoan Plasmodium and transmitted by infected female Anopheles mosquitoes. Dengue and chikungunya are caused by different viruses and transmitted by Aedes mosquitoes. A vector carries a pathogen. Explain the pathogen-vector distinction and classify the three diseases by cause, in three points. [3 marks]

1. A pathogen causes a disease, whereas a vector carries and transmits that pathogen. The mosquito and the disease-causing agent therefore perform different roles.
2. Malaria is a protozoan disease because its cause is Plasmodium. The infected female Anopheles mosquito acts as its vector.
3. Dengue and chikungunya are viral diseases. Their pathogens are viruses, while Aedes mosquitoes transmit them; sharing a vector does not make their causative agents identical.

Q3. HIV can spread through infected blood transfusions, contaminated shared needles and sexual contact. It does not spread by mere touch. Screened blood, sterile unshared needles and condoms reduce the corresponding risks. Use these facts to give three preventive measures and one reason for avoiding social exclusion. [4 marks]

1. Use screened blood for transfusion, because transfusing infected blood provides a route by which HIV can enter another person's body.
2. Use sterile needles and do not share injection equipment, because contaminated shared needles can transmit the virus between people.
3. Use safer sexual practices, including condoms, to reduce the risk associated with transmission through sexual contact.
4. Do not exclude a person merely because of HIV infection. Mere touch does not transmit HIV, so ordinary physical contact is not a reason for social rejection.

Q4. Vaccination is giving a vaccine; immunisation is developing protection. Vaccines stimulate the body's own immune response and memory, which take time to develop. Ready-made antibodies provide passive protection. Vaccines prevent disease rather than treating an established illness. Explain four distinctions or conclusions from these facts. [4 marks]

1. Vaccination describes the administration of a preparation, while immunisation describes the development of protection against a disease.
2. A vaccine stimulates active immunity because the person's own immune system responds and develops memory; this response takes time.
3. Ready-made antibodies provide passive protection rather than requiring the body to produce those antibodies first, so immunisation is broader than vaccination alone.
4. A vaccine has a preventive role. It should not be described as a medicine that treats the corresponding illness after that illness is already established.

Q5. Use these facts to explain five preventive actions: soap and water remove pathogens from hands; coughing and sneezing can spread respiratory pathogens; contaminated food and water transmit some infections; stagnant water provides mosquito breeding places; vaccines train the immune system against particular pathogens. Give one action and its purpose in each point. [5 marks]

1. Wash hands with soap and water. This removes pathogens carried on the hands and makes handwashing a practical part of personal hygiene.
2. Cover the mouth and nose while coughing or sneezing. This helps limit the spread of respiratory pathogens from the person into the surroundings.
3. Keep food and drinking water clean. This reduces exposure to pathogens through the consumption of contaminated material.
4. Prevent collections of stagnant water. Reducing mosquito breeding places helps control the vectors involved in transmission of mosquito-borne diseases.
5. Use vaccination against the appropriate diseases. Vaccines train the immune system to recognise particular pathogens and develop protection against the corresponding infections.

Q6. Smoking is associated with increased lung-cancer risk, chewing tobacco with mouth-cancer risk, and long-term alcohol or drug misuse with liver and nervous-system damage. Withdrawal can sometimes be severe enough to need medical supervision. Give three conclusions about harm and the need for help. [3 marks]

1. Both smoked and chewed tobacco are harmful: smoking is associated with increased lung-cancer risk, while chewing is associated with increased mouth-cancer risk.
2. Long-term misuse of alcohol or drugs can damage the liver and nervous system, so harm can involve internal organs as well as behaviour.
3. Withdrawal can sometimes be severe, making medical supervision necessary. A person experiencing dependence should receive suitable help rather than assuming that stopping without support is always easy.

Q7. A first-aid guide gives these rules: keep helper and casualty safe; call for trained help; cool a heat burn with running water without applying household pastes; keep a suspected fractured limb still without straightening it; after swallowed poison, seek urgent medical advice without inducing vomiting. Explain these five rules in five separate points. [5 marks]

1. Keep the scene safe so that the helper does not become another casualty and the injured person is not exposed to further danger.
2. Call for trained assistance because the casualty may need assessment and treatment beyond the helper's skills.
3. Cool a heat burn with running water to remove heat and limit damage to deeper tissues. Avoid household pastes because they can contaminate the injured area.
4. Keep a suspected fractured limb still because movement or attempted straightening can cause further injury to surrounding tissues.
5. Seek urgent medical advice after swallowed poison because treatment depends on the substance. Do not induce vomiting because vomit can enter the lungs, and corrosive substances can injure the food pipe again.

Q8. A symptom is felt by the patient; a sign can be observed or measured. Pain is felt, while raised body temperature can be measured. Classify these two observations with reasons. [2 marks]

1. Pain is a symptom because it is experienced and reported by the patient.
2. Raised body temperature is a sign because it can be measured.

Key takeaways

• Health includes physical, mental and social well-being; hygiene and healthy habits help support these connected aspects of life.
• A pathogen causes disease, while a vector carries it; Plasmodium and the female Anopheles mosquito illustrate this distinction.
• Influenza and measles spread through air, whereas malaria, dengue and chikungunya involve mosquito vectors and require mosquito-control measures.
• HIV damages the immune system but does not spread through mere touch; prevention should address its actual transmission routes.
• Immune memory produces a stronger response to the same pathogen on later exposure and forms the basis of vaccination.
• Vaccination means giving a vaccine; immunisation means developing protection, which can also include passive protection from ready-made antibodies.
• Tobacco, alcohol and habit-forming drugs can damage health; dependence and severe withdrawal may require counselling and medical help.
• First aid preserves life, prevents worsening and supports recovery while professional care is arranged; safe actions depend on the emergency.

Test yourself

What distinguishes a sign from a symptom?

A symptom is felt by the patient, such as pain. A sign can be observed or measured, such as a rash or raised temperature.

What are the pathogen and vector in malaria?

Plasmodium is the protozoan pathogen. An infected female Anopheles mosquito is the vector that introduces the parasite during a bite.

Why can mosquito control help prevent more than one disease?

Mosquitoes transmit several diseases, including malaria, dengue and chikungunya. Reducing breeding places and preventing bites help interrupt these routes of transmission.

Why should a person with HIV not be excluded from ordinary social contact?

HIV does not spread through mere touch or ordinary physical contact. Affected people need support and care rather than social exclusion.

What is the connection between vaccination and immune memory?

A vaccine stimulates an immune response and memory. On later exposure to the corresponding pathogen, the body can respond more rapidly and strongly.

Does chewing tobacco avoid tobacco's health risks?

No. Chewing tobacco is associated with increased risk of mouth cancer, while smoking has other serious harmful effects, including increased lung-cancer risk.

Why should a suspected fracture not be straightened during first aid?

Trying to straighten a fractured limb can cause further injury to surrounding tissues. Keep the injured part still and supported, and leave repositioning to medical professionals.

What are the immediate priorities after a suspected snake bite?

Call for emergency help, reassure the person, keep them still and arrange urgent medical care. A trained helper should immobilise the bitten limb.