Why Do We Fall Ill?

The World Health Organization (WHO) in 1948 defined health as follows :

Health is a state of complete physical, mental and social well-being and not merely absence of disease or infirmity.

Therefore, WHO recognizes three dimensions of health. They are :

(i) Physical well-being : It refers to physical fitness of an individual at every stage of life. It implies ‘perfect functioning’ of all the body parts i.e., various organs and organ-systems.

(ii) Mental and emotional well-being : It implies harmony between the individual and its environment. An individual should be mentally strong and able to handle the emotions.

(iii) Social well-being : Human beings are social i.e. they live in groups, regularly interacting with each other. Social health implies that every person living in a society should possess basic requirements of life i.e. a clean place of living, good earning, good food, a happy family, cooperative interaction with neighbours and friends, leading a happy and cheerful life.

1.1 PERSONAL AND COMMUNITY HEALTH

The health of an individual and that of the community are closely linked. For good health, the actions of an individual are as important as those of the other members of his community, the civic services, the industries around him, etc. The basic conditions necessary for the health of an individual and a community are :

(i) Balanced diet : A balanced diet is the first condition necessary for good health. A balanced diet is the one that provides all the nutrients required by the body in correct proportions. The nutrients required by our body are proteins, carbohydrates, fats, vitamins and minerals. When our diet lacks one or more of these nutrients, we get deficiency diseases. For example, if our diet lacks the mineral iron, we may get a disease called anaemia.

(ii) Personal hygiene : Personal hygiene is extremely important for good health. We should bathe regularly and wear clean clothes.

(iii) Clean surroundings : Our health depends on the cleanliness of our surroundings. Flies and mosquitoes carry germs that cause diseases. People fall ill quite often if the area in which they live or work has uncleaned garbage, pools of stagnant water or open drains.

(iv) Clean food and water : Disease-causing organisms and chemicals can easily enter our bodies through the food we eat and the water we drink. Fruits, vegetables and food grains may be coated with pesticides and they may carry germs, insects and eggs of worms. Therefore, these should be thoroughly washed before cooking or eating. Cooked food should be kept in clean, covered utensils. Water carries a number of disease-causing organisms. Therefore, it is best to treat water to make it safe for drinking.

(v) Clean air : Clean air is a basic requirement for good health. Breathing polluted air causes respiratory diseases such as asthma and bronchitis.

(vi) Exercise and relaxation : Regular exercise keeps us fit. People who exercise regularly are less prone to heart attacks and strokes. Exercise keeps body weight under control.

Relaxation and sleep are equally important for physical and mental health. They help in resting and recharging our bodies. They also reduce stress. We should have regular sleeping hours. We can relax by listening to music, strolling in a park, playing a game, reading and so on.

(vii) No addictions : Generally, when we talk about addiction, we mean the habit of smoking, drinking or taking drugs. An addiction causes health problems. Drinking alcohol reduces mental and physical alertness, and excessive use of alcohol may affect the nervous system and damage the liver. Smoking causes respiratory and heart diseases and cancer. Chewing tobacco can cause oral cancer and dental problems.

(viii) Good economic conditions : People who are poor cannot afford many of the things required for good health. For example, they may not be able to afford a balanced diet. Many of them live in overcrowded and unhygienic areas. They may also not have access to clean drinking water.

A disease is a disturbed state of body or mind. The term ‘disease’ means without ease or being uncomfortable. The disease can be in any part of the body organ. So, disease is defined as :

A condition of the body or some part or organ of the body in which its functions are disturbed or deranged.

2.1 DISTINCTIONS BETWEEN ‘HEALTHY AND DISEASE-FREE’

The terms ‘disease-free’ and ‘healthy’ do not convey the same meaning. A person is considered ‘disease free’ if he does not have any discomfort or derangement of the functioning of the body. However, a ‘disease free’ person can be having a good health or poor health. If a person is not suffering from a disease, it does not mean he is healthy. For an individual, the term ‘healthy’ conveys different meanings under different situations. For instance, for a dancer, healthy may mean he is able to stretch his body into difficult but graceful positions.

Therefore, a person may have a poor health without actually suffering from a particular disease.

Difference between ‘Disease-free’ and ‘Healthy’

2.2 WHAT DOES DISEASE LOOK LIKE?

A disease is the malfunctioning of some body part. Whenever there is any malfunctioning of any organ or body part, it manifests itself in the form of certain symptoms and signs. The reason for this is that each and every body part and organ of our body has specific functions and whenever anything goes wrong, it will show in some way.

2.3 DIFFERENCE BETWEEN SYMPTOMS AND SIGNS OF A DISEASE

Symptoms: It refers to the general visible changes and feelings when we feel there is something wrong. Symptoms of a number of diseases may look alike, hence symptoms do not indicate a specific disease. For example headache, loose motions, fever etc.

The symptom like headache could be due to stress, change in eyesight number, viral disease etc. There may be common symptoms of a number of diseases.

Signs : Signs of a disease means definite indications of a particular disease. On the basis of symptoms, a physician looks for specific signs of a disease. Physicians recommend specific tests on the basis of signs to identify the disease correctly.

2.4 TYPES OF DISEASES

Human diseases are classified in different ways.

Depending upon the duration for which a disease persists, diseases are grouped into two categories :

(i) Acute diseases : These diseases last for only short period of time and are severe. The acute diseases do not cause long term bad effects on our health. Examples of acute diseases are cold, cough, typhoid, cholera etc.

(ii) Chronic diseases : These diseases last for a long time, even as much as a lifetime. The chronic diseases have drastic long term effects on patient’s health. Examples of chronic diseases are diabetes, tuberculosis, elephantiasis, cardio-vascular diseases, arthritis, cancer etc.

Differences between Acute and Chronic diseases

2.4.1 Chronic disease and poor health

Long duration of a chronic disease and prolonged use of medicines during the treatment have following effects on the body :

(i) Poor functioning of some vital organs of the body : Since chronic diseases last for a long time, they generally cause damage to the vital organs of the body, like heart, lungs or kidneys. For example, lungs get severely affected during tuberculosis.

(ii) Drastic bad effects on health : Not only vital organs but general health of the body deteriorates during a chronic disease. The person may lose weight, feel fatigue and feel tired.

(iii) Prolonged general poor health : It takes long to recover from a chronic disease and so in this long process, the person has prolonged general poor health. It is also related to malfunctioning of the vital organs of the body.

(iv) Drastic long-term effects : Apart from general poor health, chronic diseases also have many other economic and financial implications which may have drastic long term effect on the person.

2.4.2 Congenital and acquired diseases

On the basis whether the diseases occur since birth or after birth, these may be classified into two types :

(i) Congenital diseases : These diseases are those which are present since birth. They are caused due to genetic abnormality or due to metabolic disorders or malfunctioning of any organ. They are permanent, generally not easily curable and may be inherited by the children. For example, haemophilia, colour blindness, sickle-cell anaemia, Down’s syndrome, etc.

(ii) Acquired diseases : These diseases are those which develop after birth. Acquired diseases can be broadly classified into two types :

(a) Communicable or infectious diseases.

(b) Non-communicable or non infectious diseases.

2.5 CAUSES OF DISEASES

When we think about the causes of diseases, we must remember that there are many levels of such causes. Let us study these causes at the following levels :

2.5.1 First Level

(i) It refers to the immediate cause i.e. to the agent that causes the disease. Viruses, bacteria, protozoans, and worms are the immediate causes.

For example, when a child suffers from loose motions, the immediate cause could be a virus or bacteria.

2.5.2 Second Level

(i) It deals with the reason of infection for the immediate cause like :

(a) Where did the viruses come from?

(b) Is it due to unclean drinking water?

(c) Why did the other children not get it?

(d) Is it due to poor health of the body?

(e) Is it due to some genetic difference that makes a child more likely to get the disease when exposed to the virus or bacteria?

(ii) It refers to the contributory causes like lack of good nourishment, genetic difference, etc.

2.5.3 Third Level

(i) This also refers to the contributory causes like:

(a) Poverty i.e., poor economic conditions.

(b) Lack of public health services that a person is exposed to.

So, poverty or lack of public health services become third level causes. Therefore, all diseases have immediate causes and contributory causes and most of the diseases have more than a single cause.

Question: Define health.

Solution: According to WHO, health is a state of complete physical, mental and social well being, and not merely an absence of disease or infirmity.

Question: Name the type of diseases that occur since birth.

Solution: Congenital diseases.

Question: What is meant by acute diseases?

Solution: Diseases that last for only very short period of time, are called acute diseases. E.g., common cold.

Question: What is meant by chronic diseases?

Solution: Ailments which last for a long time, even as much as a lifetime are termed chronic diseases. E.g., tuberculosis.

Question: Which type of disease causes more change to our body, chronic or acute? Why?

Solution: Chronic diseases because it lasts for a long time, even for whole life.

Question: State any two conditions essential for good health.

Solution: Two conditions essential for good health are :

(i) Better sanitation or clean surroundings, and

(ii) Availability of adequate and nutritious food.

Question: State any two conditions essential for being free of disease.

Solution: Two conditions essential for being free of disease :

(i) Living in clean environment.

(ii) Getting vaccinated against common infectious diseases.

Question: Why are we normally advised to take bland and nourishing food when we are sick?

Solution: When we are sick, one or more organ-systems do not function normally. As a result, we lose appetite, and do not have proper digestion and absorption of food. Sickness makes us weak. Therefore, we are advised to take bland and nourishing food during sickness.

Question: How physicians are able to pinpoint a particular disease?

Solution: First, physicians will look for signs of disease on the basis of symptoms. These signs will give a little more definite indication of the presence of a particular disease. Physicians will also get laboratory tests done such as blood test, urine test etc. to pinpoint the disease further.

Question: Differentiate between acute and chronic diseases.

Solution: Differences between acute and chronic diseases are :

Question: Differentiate between signs and symptoms of the disease.

Solution: Symptoms : It refers to the general visible changes and feelings when we feel there is something wrong. Symptoms of a number of diseases may look alike, hence symptoms do not indicate a specific disease. Examples, headache, loose motions, fever etc.

The above symptoms like headache could be due to stress, change in eyesight number, viral disease etc. There may be common symptoms of a number of diseases.

Signs : Signs of a disease means definite indications of a particular disease. On the basis of symptoms, a physician looks for specific signs of a disease. Physicians recommend specific tests on the basis of signs to identify the disease correctly.

Question: What is a health? Explain different dimensions of health. Also write down the difference between ‘healthy’ and ‘disease-free’.

Solution: Health is a state of complete physical, mental and social well-being and not merely absence of disease or infirmity.

WHO recognizes these dimensions of health. They are :

(i) Physical well-being : It refers to physical fitness of an individual at every stage of life. It implies ‘perfect functioning’ of all the body parts i.e., various organs and organ-systems.

(ii) Mental and emotional well-being : It implies harmony between the individual and its environment. An individual should be mentally strong and able to handle the emotions.

(iii) Social well-being : Human beings are social i.e. they live in groups, regularly interacting with each other. Social health implies that every person living in a society should possess basic requirements of life i.e. a clean place of living, good earning, good food, a happy family, cooperative interaction with neighbours and friends, leading a happy and cheerful life.

Difference between ‘disease-free’ and ‘healthy’ are :

Q. 1 – 5 are of one mark each.

Q. 6 – 8 are of two marks each.

Q. 9 is three marks.

Q. 10 is five marks.

1. Name any two acute diseases.

2. Name any two chronic diseases.

3. What kind of effects do chronic diseases have on our health?

4. What is meant by symptoms of a disease?

5. What is the meaning of good health for a dancer and for a musician?

6. What are the signs of a disease?

7. What are the symptoms of a disease?

8. Differentiate between congenital and acquired diseases with examples.

9. How is poor health related to chronic disease?

10. Explain the causes of diseases at various levels.

2.6 INFECTIOUS AND NON-INFECTIOUS DISEASES

The diseases could be broadly classified into two types depending on the infectious and non-infectious causes.

2.7 INFECTIOUS AGENTS

As we have read above, infectious diseases can be passed from one person to another and are caused by organisms called infectious agents.

The infectious agents could be single-celled microorganisms like viruses, bacteria and protozoans or multicellular organisms like worms. The various infectious agents are :

(i) Virus

(ii) Bacteria

(iii) Fungi

(iv) Protozoa

(v) Worm

Some common diseases caused by these infectious agents are given below in the table:

2.7.1 What is the need to know the categories of infectious agents?

It is important to know the category of the infectious agent as that helps in deciding the kind of treatment to be used to prevent or cure the disease.

Some important facts about infectious agents are :

(i) The viruses live inside the host cells whereas bacteria very rarely do.

(ii) Viruses, bacteria and fungi multiply very quickly but comparatively the worms multiply slowly.

(iii) All bacteria are closely related to each other but not to the viruses.

(iv) Many important life processes are similar in the bacteria but not in viruses.

2.7.2 Why do antibiotics work against bacteria but not against viruses?

(i) Antibiotics and bacteria : We often take antibiotics when suffering from bacterial infections. Antibiotics work in the following way :

Antibiotics commonly block important biochemical pathways of bacteria. For example, many bacteria make a cell-wall to protect them. The antibiotic blocks the biochemical pathways that build the cell wall. Hence, the bacteria are unable to make the cell wall and die away.

(ii) Antibiotics and Viruses : Antibiotics are not effective against viruses.

Viruses do not have the metabolic pathways as found in bacteria. Instead, viruses make use of the machinery and pathways of the host cell. Hence, antibiotics do not work against viral infections. For example, common cold is due to the viral infection. Now, if we take antibiotics during the viral cold, it is of no help. However if the bacterial infection also sets in along with the cold, the antibiotic will work only against the bacterial part of infection, not the viral infection.

2.8 MEANS OF SPREAD

Since the infectious diseases can spread from a diseased person to a healthy person, they are also called as communicable diseases. The various means of spread are -

(i) Direct Contact : An infectious disease can spread by direct contact between the infected and the healthy person. It includes diseases like chicken pox, common cold etc. Direct contact or contact with the discharge from the sores, skin or infectious membranes cause the infection.

(ii) By Air : For the diseases that spread through air, tiny droplets are sufficient to cause an infection. The little droplets get thrown into air when an infected person sneezes, coughs or spits. They are laden with bacteria and viruses. By inhaling this air containing the droplets, one gets the infection. Example, like common cold, pneumonia, tuberculosis and influenza.

Showing potential risk of getting air-transmitted diseases as we move closer to the infected person. In closed areas, the droplet nuclei recirculate and pose a risk to everybody. Thus, overcrowded and poorly ventilated housing is a major factor in the spread of airborne diseases.

(iii) By Water : The diseases through water spread, when the excreta of an infected person suffering from an infectious disease like cholera, gets mixed with the drinking water. When people drink this contaminated water, they also get infected. Diseases of alimentary canal like typhoid, and cholera get transmitted this way.

(iv) Through contamination of food : The bacteria that cause infection of alimentary canal like dysentery, typhoid and Salmonella food poisoning are passed out in the faeces of infected person. They reach the food through unwashed hands, and enter the body through mouth.

(v) Sexually transmitted diseases : Syphillis, gonorrhoea and AIDS are sexually transmitted diseases (STD). They spread by sexual contact with the infected person. They do not spread by casual physical contact like handshake, hugs or sports like wrestling or by any other way in which we touch each other socially. For example, AIDS is a sexually transmitted disease. It can also spread through blood to blood contact (blood transfusion or using the same infected needle) with the infected person. If a mother has the disease, the infected mother can pass it to her baby during pregnancy or through breast feeding.

(vi) By Vector : Many times the transmission of the infecting agent to a healthy person is not direct but through an intermediary agent, called the vector or carriers.

The common vectors are insects like cockroaches, houseflies, mosquitoes etc.

Malaria spreads through female Anopheles mosquito. The female Anopheles carries the malarial parasite in its salivary glands which gets transferred during mosquito bite.

In many species of mosquitoes, the females feed on the blood of warm-blooded animals. In this process, they transfer the diseases from one person to another.

(vii) By bite of an animal : Rabies or hydrophobia in man is caused by a virus that is transmitted through a dog bite. The virus is present in the saliva of the rabid animal and enters the healthy person through the wound.

Common methods of transmission of diseases.

2.9 ORGAN-SPECIFIC AND TISSUE-SPECIFIC MANIFESTATIONS

The disease-causing microbes enter the body through different means like:

(a) Nose, (b) Mouth, (c) Sexual contact, (d) Skin, (e) Blood etc.

Since these microbes enter the body through different parts, they reach different organs and tissues of the body where they cause infection.

Their point of entry in the body is directly related to the organ or tissue they infect. This can be understood by studying some examples given in the table.

2.10 TISSUE-SPECIFIC MANIFESTATIONS

The signs and symptoms of the disease depend on the tissue or the organ, the infectious agent or microbe targets.

2.11 COMMON EFFECTS OF DISEASES

(i) Along with tissue-specific manifestations of the diseases, there are some common effects of the diseases too. Since these effects occur in many diseases, they do not point towards any specific disease, for example fever and headache are common to a number of diseases.

(ii) Common effects are due to the fact that the body’s immune system gets activated, the moment an infection occurs in the body.

(iii) The activated immune system involves a number of cells which are sent to the affected organ to kill the disease causing microbes. This recruitment process of the active immune system is called inflammation.

(iv) This process of inflammation of the affected organ leads to both local and general effects.

Local effects are swelling and pain of the infected area.

General effect is fever (rise in temperature of the whole body).

2.12 IMMUNE SYSTEM AND AIDS

Acquired Immuno Deficiency Syndrome commonly called AIDS is a fatal disease. It was first detected in USA in June 1981.

2.12.1 Cause

It is caused by a retrovirus HIV (human immuno deficiency virus). This virus attacks the white blood cells in the human blood and therefore weakens the human body’s immunity or self-defence mechanism.

Structure of HIV or AIDS virus

2.12.2 Modes of transmission

AIDS is transmitted only by the contact of infected cells containing blood of a patient with the blood of a healthy person. It spreads through :

(i) Unprotected sexual intercourse with an infected partner.

(ii) Use of contaminated needles and syringes to inject drugs or vaccines.

(iii) Use of contaminated razors for shaving.

(iv) Use of contaminated needles for boring pinnae,

(v) Transfusion of infected blood or blood products.

(vi) Organ transplant.

(vii) Artificial insemination.

(viii) Mother to baby due to rupturing of blood vessels at the time of birth.

2.12.3 Symptoms

Since AIDS virus destroys the protective immune system of the body, the body can no longer fight back many minor infections that we encounter every day. The person becomes susceptible to other infections and diseases like pneumonia, tuberculosis and certain cancers. For example, the person suffering from AIDS cannot fight back common cold, and it may become pneumonia. A minor gut infection can lead to diarrhoea. The person may have persistent cough and fever and ultimately these infections may kill the people suffering from AIDS.

Check Out- CBSE Class 9 Science Notes

Common symptoms of AIDS include :

(i) Sweating at night and weight loss.

(ii) Swollen lymph nodes.

(iii) Ulcers, repeated diarrhoea, prolonged cough.

(iv) Decreased count of blood platelets resulting in haemorrhage.

(v) Continuous fever.

(vi) Severe brain damage. It may lead to loss of memory, speech and thinking ability.

(vii) Susceptibility to other infections.

2.12.4 Treatment

Till date, there is no specific treatment against HIV infection.

Question: Expand the term AIDS.

Solution: Acquired Immuno Deficiency Syndrome.

Question: What are the two distinct categories of diseases? Give example.

Solution: (i) Infectious disease e.g., tuberculosis.

(ii) Non-infectious disease e.g., high blood pressure.

Question: Name the bacteria which causes peptic ulcer.

Solution: Helicobacter pylori.

Question: How bacteria protect themselves?

Solution: They make a cell wall to protect themselves.

Question: How antibiotic penicillin affects bacteria?

Solution: It blocks the bacterial processes that build the cell-wall, as a result, the bacteria dies.

Question: Give one example of each of the following:

(i) Disease which spreads through air.

(ii) Disease which speads through water.

(iii) Disease which speads through insect.

Solution: (i) Common cold (other examples are pneumonia and tuberculosis).

(ii) Hepatitis (other examples are jaundice, typhoid and cholera).

(iii) Malaria (other examples are dengue fever, sleeping sickness and Japanese encephalitis).

Question: What is inflammation? What are the local and general effects due to inflammation?

Solution: The activated immune system involves a number of cells which are sent to the affected organ to kill the disease causing microbes. This recruitment process of the active immune system is called inflammation.

Local effects are swelling and pain. General effect includes fever.

Question: Apart from sexual contact AIDS virus can spread through which other means?

Solution: The other means through which AIDS can spread are:

(i) Blood to blood contact.

(ii) Infected mother to her baby during pregnancy.

(iii) Through breast feeding.

Question: Differentiate between infectious and non-infectious diseases.

Solution: The differences between infectious and non-infectious diseases are:

Question: What will be the signs and symptoms of diseases if the following organs of our body are targeted by microbes?

(a) Lungs (b) Liver (c) Brain

Solution: (a) Cough and breathlessness

(b) Jaundice

(c) Headaches, vomiting, fits or unconsciousness.

Question: Do all microbes go to the same tissue or organ or do they go to different ones. If they go to different organs, how they damage it?

Solution: Different microbes can go to different organs and damage it.

Their point of entry in the body is directly related to the organ or tissue they infect. This can be understood by studying some examples given in the table.

Q. 1 – 5 are of one mark each.

Q. 6 – 8 are of two marks each.

Q. 9 – 10 are three marks each.

Q. 11 is of five marks.

1. Name two non-communicable diseases.

2. Name three diseases that can be prevented by drinking safe water.

3. Name two diseases caused by protozoa.

4. Name a viral disease which suppresses the body’s immune mechanism.

5. Which organism causes ringworm infection?

6. A child is suffering from acute diarrhea and vomiting. What deficiency may result due to this condition? What precaution must be taken to avoid it?

7. Why antibiotics do not harm the animal cells?

8. Differentiate between infectious and non-infectious diseases.

9. The body of a patient has lost its power of fighting against infections. Which disease may the patient be suffering from? Name the pathogen and describe any two modes of its transmission from the patient to other persons.

10. Explain the different means of spread of diseases.

11. The point of entry of an microbe is directly related to the organ / tissue they infect. Explain with examples.

2.13 PRINCIPLES OF TREATMENT

There are two ways to treat an infectious disease :

(i) Reduce the effects of the disease : For this, we take treatment to have some relief from the discomfort caused by the disease i.e.

(a) Take medicines that bring down fever or pain.

(b) Take bed rest to conserve the energy so that body can use energy for healing.

(ii) Kill the cause of the disease : In this, one takes the symptom-directed treatment and take medicines that kill microbes.

2.13.1 How do we kill microbes?

The microbes are of various types like bacteria, viruses, fungi and protozoa. Each one may need different medicines to kill the microbe.

Each group of organisms has some essential bio-chemical life processes that are specific to that group and not shared by other groups. These are used to kill the microbes.

2.13.2 Antibiotics

An ideal drug to cure a disease is the one that blocks the chemical pathway of the infecting agent without harming the host.

Antibiotics are such drugs that are used to cure bacterial infection.

Antibiotics cause the bacterial cell walls to break down by interfering with the biochemical path way that maintains it. Since these processes do not occur in animal cells, the animal tissues remain unaffected.

2.13.3 Drugs against viruses

There are very few effective drugs against viruses. It is because viruses have very few biochemical mechanisms of their own. They enter the cells and use the cell’s machinery for their life processes. Hence, there are very few virus-specific targets to aim at. The virus is so closely involved in its host cell’s physiology that any chemical that harms the virus will also harm the cell.

Despite the limitations, scientists have developed some effective anti-viral drugs.

2.14 PRINCIPLES OF PREVENTION

While treating an infectious disease, following three limitations are normally confronted:

(i) Once a person has a disease, some of the body functions may get damaged and may not recover completely.

(ii) The treatment of the disease always takes time, which means the person suffering from the disease is confined to bed or incapable of normal routine till proper treatment is given and the person recovers.

(iii) The person suffering from the infectious disease can serve as a source from where the infection may spread to other people.

Keeping in view these limitations, we can understand that prevention of diseases is much better than this cure. Preventing measures are precautionary measures taken to check the transmission of infectious diseases.

2.15 WAYS OF PREVENTION OF INFECTIOUS DISEASES

There are two ways of prevention of infectious diseases :

(i) General ways

(ii) Specific ways

2.15.1 General ways of prevention

It relates to preventing the exposure to the infectious microbes. These include :

(i) Prevention by keeping the environment clean : The basic key to the prevention of infectious disease is by keeping clean environment and good public hygiene.

(a) For air borne microbes, we can prevent exposure by providing living conditions that are not overcrowding.

(b) For water-borne microbes, we can prevent drinking unsafe water. Water should be treated to kill the infectious microbes.

(c) For vector-borne infections, we can provide clean environment like clean, covered and hygienic food and drinks.

(d) We should not allow mosquito breeding, by keeping the drains clean or spraying with kerosene.

(ii) Proper and sufficient food : For a good immune system, it is important to have a healthy body. It means one should eat proper, balanced and sufficient food for a good active immune system.

(iii) Sterilization : Patient’s surroundings and articles of use should be sterilized. Soap, phenyl, dettol, and antiseptic lotion may be used wherever necessary.

(iv) Isolation : A person suffering from an infectious disease should be segregated so that others do not catch infection from him.

(v) Education : People should be educated about the infectious diseases so that they may protect themselves against such infections.

2.15.2 Specific ways of prevention

It refers to a part of our immune system that reacts against specific microbes, recognizes them and kills them.

IMMUNITY

Immunity is the capacity of the body to defend against the disease. Immunity can also be defined as the ability of the body to resist the disease.

The immunity can be of two types :

(i) Natural or In-born

(ii) Acquired

(a) Natural or In-born immunity : It refers to the immunity present at the time of birth. During the development of the child, some antibodies from the mother pass through the placenta to the foetus. They protect the young child from number of diseases like measles and polio till body’s own immune system becomes functional.

(b) Acquired immunity : It is the immunity acquired after birth. It could be active or passive.

(i) Active immunity : It can be natural or artificial.

(a) Natural active immunity : When the body is exposed to an antigen for the first time, it contracts the disease. The body not only produces antibodies, but also large number of memory cells. When the antigen strikes the second time, the memory cells produce large number of antibodies and the body does not contract a disease. It may last for a life time. This is the reason why some childhood diseases like measles, mumps, chicken pox etc., occur only once in a life time.

(b) Artificial active immunity : It is produced by injecting a small quantity of an antigen called the vaccine into the body. The process is called as immunization or vaccination. In active immunity the body manufactures the antibodies against the antigen and that is why such immunity lasts and protects the animal for a long time.

(ii) Passive Immunity : In this immunity, the organisms own body does not produce the antibodies, instead readymade antibodies from some other organism are introduced for protection against the disease. For protection against tetanus, diphtheria, rabies or Salmonella, the disease causing bacteria or virus is introduced into another animal like horse or sheep. Antibodies soon appear in the horse’s or sheep’s blood. From there, the antibodies are extracted and injected into humans to provide the passive immunity. Such immunity is short lived.

2.15.3 Vaccines

Antibody provoking agents are termed vaccines. The term vaccine is used for a preparation of antigenic proteins of pathogens or weakened or dead pathogens which on inoculation into a healthy person provides temporary or permanent immunity against the disease by inducing antibodies formation. Now, vaccines are available for preventing whole range of infectious diseases, e.g., tetanus, diptheria, whooping cough, measles, polio, hepatitis-B, cholera, tuberculosis, measles, plague, mumps etc. These form the public health programme of childhood immunization for preventing infectious diseases.

Vaccines against some common diseases are mentioned in the table below :

2.16 COMMON MICROBIAL DISEASES AND THEIR PREVENTION

The causative agent, symptoms, control and preventive measures of some common diseases are given below :

2.17 PULSE POLIO PROGRAMME

‘Pulse polio immunization programme’ was launched in 1995-1996 with an aim to eradicate polio disease from the world. It involves simultaneous administration of polio drops (polio vaccine) to whole of the high risk population (i.e., children under three years of age) on a single day throughout the nation.

This programme uses oral polio vaccine or OPV. As per the National Immunisation Schedule (NIS), a dose of 3 drops (0.5 ml) is given orally to the child, i.e., one dose each at 1.5, 2.5 and 3.5 month’s age. Finally, a booster dose is given at the age of 1.5 years.

A boy being given the polio drops under the Pulse Polio Programme

Aims :

(i) To immunize those children who are not earlier immunized or are partially immunized.

(ii) To boost the immunity of children already immunized.

(iii) To replace the disease-causing wild virus by harmless vaccine virus in the environment.

Question: Who gave the first idea of vaccination?

Solution: Dr. Edward Jenner

Question: Name the diseases showing respective symptoms:

(i) Yellowness in the sclera of eyes and skin.

(ii) Patient fears from water.

Solution: (i) Hepatitis

(ii) Rabies.

Question: Expand ORS.

Solution: Oral rehydration solution.

Question: Name the causative organism and vector of malaria.

Solution: Causative organism is Plasmodium and vector is female Anopheles mosquito.

Question: Name any one general way of prevention of infectious diseases.

Solution: Eradication of vectors.

Question: Name the most common insect that carries causative organisms of cholera, typhoid, dysentery and tuberculosis.

Solution: Housefly.

Question: What is immunization?

Solution: Immunization is a technique in which people are given particular vaccine so that they develop temporary or permanent immunity against a particular infectious disease. In other words, immunization is a specific way of preventing infectious diseases.

Question: After eating food, number of people complained of nausea, vomiting, abdominal pain and loose stools with blood and mucus. Name the disease they are suffering from? Also, name the causative organism.

Solution: Disease they might be suffering from is diarrhoea. Bacteria responsible for causing diarrhoea can be Escherichia coli or Salmonella.

Question: Name the plant and its part which is used to extract important antimalarial drug. Name the drug also.

Solution: (i) Bark of Cinchona plant. (ii) Quinine drug.

Question: What is the general way of preventing infections?

Solution: The general way of preventing infections mostly relate to preventing exposure. They are :

(i) For air-borne infection, overcrowded conditions are to be prevented.

(ii) For preventing water-borne infections, one should use safe drinking water only.

(iii) For vector-borne infections, breeding of vector should be prevented by keeping the environment clean.

Question: What is immunity? What is immunization and vaccine? Why some childhood diseases (like chicken pox) occur only once in a life time? Name the diseases for which the following vaccination are given: DPT, Hepatitis-B, OPV, BCG.

Solution: (i) Immunity is the capacity of the body to defend against the diseases.

(ii) Immunization is stimulating the body to produce antibodies by artificial means.

(iii) A vaccine is a preparation of weakened infectious agents or their products that can be injected or given orally to prevent specific diseases.

(iv) When the body is exposed to an antigen for the first time, it contracts the disease. The body not only produces antibodies, but also large number of memory cells. When the antigen strikes the second time, the memory cells produce large number of antibodies and the body does not contract a disease. It may last for a life time. This is the reason why some childhood diseases like measles, mumps, chicken pox etc., occur only once in a life time.

(v) The name of the diseases are mentioned in the table below :

Q. 1 – 5 are of one mark each.

Q. 6 – 8 are of two marks each.

Q. 9 – 10 are three marks each.

Q. 11 is of five marks.

1. Name the disease the child will not suffer from if BCG vaccine is given.

2. Name the causative organism for T.B.

3. Why rabies is also called as hydrophobia?

4. Name any causative organism of diarrhea.

5. List a method of preventing vector borne infections.

6. How do memory cells help in immunization?

7. List two basic ways to treat an infectious disease.

8. What is passive immunity?

9. Write three difficulties faced to cure a infectious disease.

10. Explain how can we prevent diseases?

11. Write about the causative organism, symptoms and prevention of the following diseases:

(a) Hepatitis.

(b) Rabies.