CBSE Class 9 Science Why do we fall ill Notes

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HEALTH AND ITS FAILURE

Why do we fall ill is a Class 9 Science chapter on health and its failure. These notes cover the World Health Organisation definition of health, community health services, the conditions essential for good health, the difference between healthy and disease-free, acute and chronic diseases, chronic diseases such as heart disease, stroke, cancer, diabetes and chronic respiratory diseases, infectious and non-infectious causes, the means of spread of infectious diseases, prevention, immunisation, the major bacterial, viral, fungal and parasitic diseases, and the intext and exercise questions with answers.

Topics Covered

1. Health and its Failure
2. Conditions Essential for Good Health
3. Personal and Community Issues Both Matter for Health
4. Distinctions between Healthy and Disease-free
5. Disease and its Causes
6. Acute and Chronic Diseases
7. Chronic Diseases and Poor Health
8. Infectious and Non-Infectious Causes
9. Means of Spread of Infectious Diseases
10. Principles of Treatment and Prevention
11. Immunisation
12. Supplementary Notes on Infectious Agents and Diseases
13. Intext and Exercise Questions

HEALTH AND ITS FAILURE

Good health is a very hard thing to measure, but it is one of life's most precious things. The World Health Organisation has defined health as a state of complete physical, mental and social well-being.

Community health can be defined as "All the personal health along with the environmental services for the importance of health of community".

Some of the health services are given below:
(i) Establishment of health care services like primary health centres, district hospitals, community health centres, medical colleges, All India Institutes, regional hospitals, etc.
(ii) Provision of safe drinking water and proper disposal of garbage.
(iii) Prevention of harmful insect breeding sites.
(iv) Management of different types of environmental pollution by Central and State Pollution Control Boards.
(v) Preventive vaccinations against a number of diseases like tuberculosis, diphtheria, whooping cough, tetanus, measles, hepatitis, etc.
(vi) Provision of family planning advice and services.
(vii) Provision of medical care to school-going children.
(viii) Prevention of food adulteration.
(ix) Health education.

CONDITIONS ESSENTIAL FOR GOOD HEALTH

There are several conditions which have to be fulfilled for good health. The important ones are:
(i) Nutrition,
(ii) Proper habits, and
(iii) Exercise and relaxation.

[Figure: Conditions for good health, shown as a box at the top with three boxes below it: Nutrition, Proper habits, and Exercise and Relaxation]

(i) Nutrition
Nutrition can be defined as the procurement of substances necessary for growth, development, maintenance and activities of a living organism. We obtain food from various plant and animal sources. In order to keep healthy and energetic, we need to take food. It takes care of the daily energy need also. We consume energy even while sleeping. Energy requirement depends on the individual, age and special needs. Growing children, pregnant women and nursing mothers need more energy.

(ii) Proper Habits
Another important aspect of good health is to observe proper dietary habits, that is, consumption of a balanced diet at fixed times. Good personal and domestic hygiene is very essential. Take full care of the following aspects:
Your food should be fresh and kept away from dust, flies, insects and microbes to avoid any infection and spoilage.
Utensils should be kept clean.
You should wash your face and hands with soap before eating or handling food.
Food should be cooked with good feelings and in a cheerful state.
Smoking, chewing tobacco, drinking alcohol and taking addictive drugs are bad habits and should be avoided. They can have damaging effects on our body and mind.

(iii) Exercise and Relaxation
Regular exercise is necessary to keep our body fit. These exercises vary with age, physical condition and nature of work of the individual. In the case of a sedentary worker, exercise is even more essential. Another aspect of health is regular sleep and relaxation. The duration of sleep also varies with age and nature of work. Infants sleep for long hours, which is necessary for them to grow. For children, an average of eight hours of sound sleep is sufficient. For adults, six hours of sleep is enough. Relaxation improves the capacity to work. Relaxation may be defined as an activity or recreation which provides relief or diversion from work or effort. There are various ways of relaxation. Yoga and meditation relax the body and mind. Listening to music and reading magazines are also relaxing.

PERSONAL AND COMMUNITY ISSUES BOTH MATTER FOR HEALTH

Health is a state of physical, mental and social well-being. The conditions necessary for good health are:
i) Good physical and social environment.
ii) Good economic conditions.
iii) Social equality and harmony.

Good physical and social environment includes clean surroundings, good sanitation, proper garbage disposal and clean drinking water.

Good economic conditions include job opportunities for all, so that people can earn enough to have nutritious food and lead a healthy life.

Social equality and harmony are necessary for a healthy and peaceful life.

[Figure: Diagram of the factors that shape health and illness, with Health and illness at the centre. Psychological factors (thoughts and actions, feelings, stress, beliefs) on the top, Biological characteristics (genetic predispositions, exposure to germs, brain and other nervous system) on the left, Social conditions (environments, cultural influences, family relationships, social support) on the right]

DISTINCTIONS BETWEEN 'HEALTHY' AND 'DISEASE-FREE'

DISEASE AND ITS CAUSES

A person may be regarded as suffering from a disease when his body does not function properly. Minor and major disorders of the body may lead to diseases. Infectious diseases are caused by germs. One of the greatest achievements in the history of mankind is the demonstration by Pasteur, Koch and others of germs or microbes that cause diseases. Microbes are microscopic organisms such as viruses, bacteria, some fungi and protozoans that are responsible for causing diseases in human beings. Cholera, tetanus, typhoid, diphtheria and pneumonia are some common diseases caused by bacteria. Polio, common cold, influenza, measles, chicken pox and AIDS are diseases caused by viruses. Amoebic dysentery and malaria are caused by protozoans.

ACUTE AND CHRONIC DISEASES

When a person is affected by a disease, either the normal functioning or the appearance of one or more systems of the body changes for the worse. These changes give rise to signs of the disease called symptoms. On the basis of the symptoms, physicians look for the signs of a particular disease and conduct tests to confirm the disease.

Types of diseases:
i) Acute diseases: These are diseases which last only for a short period of time and do not have a long-term effect on health. Eg: Cold, cough, typhoid, cholera, etc.
ii) Chronic diseases: These are diseases which last for a long time and have a long-term drastic effect on health. Eg: Diabetes, tuberculosis, elephantiasis, arthritis, cancer, etc.

Difference between Acute Disease and Chronic Disease

CHRONIC DISEASES AND POOR HEALTH

A chronic disease is a disease that persists for a long time. Chronic diseases are the major cause of death and disability worldwide. The total number of people dying from chronic diseases is double that of all infectious diseases (including HIV/AIDS, tuberculosis and malaria), maternal and parental conditions, and nutritional deficiencies combined. 80% of chronic disease deaths occur in low and middle income countries, and half are in women. Without action to address the causes, deaths from chronic disease will increase by 17% between 2005 and 2015.

Chronic diseases
Cardiovascular diseases, mainly heart disease and stroke
Cancer
Chronic respiratory diseases
Diabetes
Genetic disorders
Others, such as mental disorders, vision and hearing impairment, oral diseases, bone and joint disorders

[Figure: Causes of chronic diseases flow chart. Socioeconomic, Cultural, and Environmental Determinants (Globalization, Urbanization, Population Ageing) lead to Individual-specific Modifiable Risk Factors (Unhealthy Diet, Physical Inactivity, Tobacco Use) and Individual-specific Non-Modifiable Risk Factors (Age, Heredity). Both lead to Biochemical/Physiological Risk Factors (Raised Blood Pressure, Raised Blood Glucose, Abnormal Blood Lipids, Overweight/Obesity), which lead to Main Chronic Diseases: Cancer, Heart Disease, Stroke, Chronic Respiratory Diseases, Diabetes]

[Figure: Tree titled with the chronic diseases as fruits: Cancer, Chronic lung diseases, Diabetes, Heart disease and stroke, and Other NCDs. The roots are Physical inactivity, Alcohol abuse, Tobacco and Unhealthy diet]

Heart disease: There are many forms of heart disease. Coronary heart disease, also known as coronary artery disease or ischaemic heart disease, is the leading cause of death globally. It is caused by disease of the blood vessels (atherosclerosis) of the heart.

Stroke: Stroke is a disease of the brain caused by interference with the blood supply. Stroke and heart disease are the main cardiovascular diseases.

Cancer: Cancer describes a range of diseases in which abnormal cells proliferate and spread out of control. Other terms used are tumours and neoplasms. There are many types of cancer, and all organs of the body can become cancerous.

Chronic respiratory diseases: Diseases of the lung take many forms. Chronic obstructive respiratory disease and asthma are the most common forms. Chronic obstructive respiratory disease is caused by irreversible obstruction of the larger airways in the lung. Asthma is caused by reversible obstruction of the smaller airways in the lung.

Diabetes: Diabetes is characterised by raised blood glucose (sugar) levels. This results from a lack of the hormone insulin, which controls blood glucose levels, and/or an inability of the body's tissues to respond properly to insulin. The most common type of diabetes is type 2, which accounts for about 90% of all diabetes and is largely the result of excessive weight and physical inactivity. The usual childhood form of diabetes (type 1 diabetes) is caused by an absolute lack of insulin. Without insulin, type 1 diabetes is rapidly fatal.

What causes chronic diseases?
The causes (risk factors) of chronic diseases are well established and well known. A small set of common risk factors is responsible for most of the main chronic diseases. These risk factors are modifiable and the same in men and women:
unhealthy diet;
physical inactivity;
tobacco use.

These causes are expressed through the intermediate risk factors of raised blood pressure, raised glucose levels, abnormal blood lipids, overweight and obesity. The major modifiable risk factors, in conjunction with the non-modifiable risk factors of age and heredity, explain the majority of new events of heart disease, stroke, chronic respiratory diseases and some important cancers. The relationship between the major modifiable risk factors and the main chronic diseases is similar in all regions of the world.

Other risk factors: Many more risk factors for chronic diseases have been identified, but they account for a smaller proportion of disease. Harmful alcohol use is an important contributor to the global burden of disease, but its relationship to chronic disease is more complex. Other risk factors for chronic disease include infectious agents that are responsible for cervical and liver cancers, and some environmental factors, such as air pollution, which contribute to a range of chronic diseases including asthma and other chronic respiratory diseases.

Psychosocial and genetic factors also play a role
Childhood risk: There is now extensive evidence from many countries that conditions before birth and in early childhood influence health in adult life. For example, low birth weight is now known to be associated with increased rates of high blood pressure, heart disease, stroke and diabetes.
Risk accumulation: Ageing is an important marker of the accumulation of modifiable risks for chronic disease. The impact of risk factors increases over the life course.
Underlying determinants: The underlying determinants of chronic diseases are a reflection of the major forces driving social, economic and cultural change: globalization, urbanization, population ageing and the general policy environment.
Poverty: Chronic diseases and poverty are interconnected in a vicious circle. Poverty and the worsening of already existing poverty are caused by chronic diseases. The poor are more vulnerable for several reasons, including greater exposure to risks and decreased access to health services. Psychosocial stress also plays a role.

INFECTIOUS AND NON-INFECTIOUS CAUSES

Infectious diseases (communicable diseases) are diseases which spread from an infected person to a healthy person through air, water, food, vectors, physical contact or sexual contact. Eg: Common cold, chicken pox, mumps, measles, typhoid, cholera, tuberculosis, malaria, AIDS, etc.

Non-infectious diseases (non-communicable diseases) are diseases which are not spread from an infected person to a healthy person. Eg: Beri beri, rickets, scurvy, night blindness, diabetes, cancer, high blood pressure, etc.

Causes of diseases
Diseases are caused by:
i) Pathogens like viruses, bacteria, fungi, protozoans or worms.
ii) Poor health and under nourishment.
iii) Malfunctioning of body parts.
iv) Environmental pollution.
v) Genetic disorders.

INFECTIOUS AGENTS

Infectious diseases are caused by microorganisms such as viruses, bacteria, fungi or parasites, and can spread between individuals. Microorganisms that cause disease are collectively called pathogens.

Pathogens cause disease either by disrupting the body's normal processes and/or by stimulating the immune system to produce a defensive response, resulting in high fever, inflammation and other symptoms. Infectious diseases can be spread from one person to another, for example through contact with bodily fluids, by aerosols (through coughing and sneezing), or via a vector, for example a mosquito.

Infectious diseases can be caused by:
Bacteria: These one-celled organisms are responsible for illnesses such as strep throat, urinary tract infections and tuberculosis.
Viruses: Even smaller than bacteria, viruses cause a multitude of diseases, ranging from the common cold to AIDS.
Fungi: Many skin diseases, such as ringworm and athlete's foot, are caused by fungi. Other types of fungi can infect your lungs or nervous system.
Parasites: Malaria is caused by a tiny parasite that is transmitted by a mosquito bite. Other parasites may be transmitted to humans from animal faeces.

[Figure: Diseases caused by Infectious agent, branching into five groups. Bacterial diseases (Example: Typhoid, Cholera, Tuberculosis, Acne, Anthrax). Fungal diseases (Common Cold, Influenza, Dengue fever, AIDS, Japanese encephalitis or brain fever). Viral diseases (Skin diseases). Protozoan diseases (Malaria (Plasmodium), Kalaazar (Leishmania), Sleeping sickness (Trypanosomes)). Worm diseases (Ascariosis (Roundworm), Elephantiasis (Wuchereria))]

MEANS OF SPREAD

Infectious diseases spread from an infected person to a healthy person through air, water, food, vectors, physical contact and sexual contact.

i) Through air: Common cold, tuberculosis, pneumonia, etc.
ii) Through water: Cholera, amoebic dysentery, etc.
iii) Through vectors: Mosquitoes: Malaria, dengue, yellow fever, etc. Flies: Typhoid, tuberculosis, diarrhoea, dysentery, etc.
iv) Through sexual contact: Syphilis, AIDS. The AIDS virus can also spread through blood transfusion and from the mother to her child during pregnancy and through breast feeding.

The figure below shows how air-transmitted diseases are easier to catch the closer we are to the infected person. However, in closed areas, the droplet nuclei recirculate and pose a risk to everybody. Overcrowded and poorly ventilated housing is therefore a major factor in the spread of airborne diseases.

[Figure: Air-transmitted diseases. A person releases small droplets which evaporate to droplet nuclei in this zone. Large droplets settle to the ground in a few seconds, within about 2 m. Droplet nuclei are carried in air currents for minutes to hours, reaching about 4 m, and are shown recirculating through the room with Ventilation]

Disease can also be spread through water. This occurs if the excreta from someone suffering from an infectious gut disease gets mixed with water. For example, cholera gets mixed with the drinking water used by people living nearby. The cholera-causing microbes will enter new hosts through the water they drink and cause disease in them. Such diseases are much more likely to spread in the absence of safe supplies of drinking water.

Surprisingly, there are microbial diseases such as syphilis or AIDS that are transmitted by sexual contact from one partner to the other. However, such sexually transmitted diseases are not spread by casual physical contact. Casual physical contacts include handshakes, hugs, sports like wrestling, or any of the other ways in which we touch each other socially. Other than sexual contact, the AIDS virus can also spread through blood-to-blood contact with infected people, or from an infected mother to her baby during pregnancy or through breast feeding.

[Figure: Common methods of transmission of diseases. An infected person spreads disease to a healthy person by Direct contact, By air, Indirect contact (shared cups and clothes), By food, By water, and Mosquito/Insect. A rabid animal is also shown as a source]

The sexual act is one of the closest physical contacts two people can have with each other.

ORGAN-SPECIFIC AND TISSUE-SPECIFIC MANIFESTATIONS

Disease-causing microbes enter the body by different means and go to different organs and tissues.
Microbes which enter through the nose are likely to go to the lungs (bacteria which cause tuberculosis of the lungs).
Microbes which enter through the mouth are likely to stay in the gut (bacteria which cause typhoid) or the liver (bacteria which cause jaundice).
The virus which causes AIDS enters the body through sexual organs during sexual contact, spreads through the lymph to all parts of the body and damages the immune system.
Malaria-causing microbes, entering through a mosquito bite, go to the liver and then to the red blood cells.
The virus causing Japanese encephalitis, or brain fever, enters through a mosquito bite and infects the brain.

PRINCIPLES OF TREATMENT

The treatment of infectious diseases consists of two steps: reducing the effects of the disease (symptoms) and killing the microbes which caused the disease.
i) To reduce the effects of the disease: This can be done by taking medicines to bring down the effects of the disease, like fever, pain or loose motions, and by taking bed rest to conserve energy.
ii) To kill the microbes: This can be done by taking suitable antibiotics and drugs which kill the microbes, so that the disease is cured.

PRINCIPLES OF PREVENTION

There are two ways of preventing infectious diseases: general ways and specific ways.
i) General ways of prevention: Public hygiene is the most important for prevention of infectious diseases. Proper and sufficient food for everyone will make people healthy enough to resist infection. Airborne diseases can be prevented by living in conditions that are not crowded. Waterborne diseases can be prevented by providing safe drinking water. Vector-borne diseases can be prevented by providing a clean environment.
ii) Specific ways of prevention: The specific way to prevent infectious diseases is immunisation by taking vaccines. Vaccines provide immunity from infectious diseases like tetanus, diphtheria, whooping cough, measles, polio, etc. Our body has an immune system which fights microbial infection. When this system first sees an infectious microbe, it kills the microbe and remembers it. So if the microbe enters the body the next time, the body responds more vigorously. Vaccines mimic the infectious microbe, strengthen our immune system and protect the body from infectious diseases.

IMMUNISATION

Immunisation gives a very good level of protection against many serious diseases. It uses your body's natural defence mechanism, the immune response, to build resistance to specific infections.

There are three reasons why we immunise children.
First, immunisation prevents children from becoming ill with unpleasant and serious infectious diseases, which have a risk of complications and long-term side effects.
Second, we immunise to help protect all children in the population. The more people who are immunised, the less of the infectious disease there is around, so the less chance there is of anyone catching it. When levels of immunisation against an infectious disease are really, really high, something happens called 'herd immunity', where the risk of the disease occurring is so low that even those who cannot be immunised are unlikely to be affected.
Third, we immunise to try and wipe out as many infectious diseases as we can, everywhere in the world.

[Figure: National Immunization Schedule]

SUPPLEMENTARY NOTES

CAUSES OF INFECTIOUS DISEASES (INFECTIOUS AGENTS)

VIRUSES

Viral diseases are extremely widespread infections caused by viruses, a type of microorganism. There are many types of viruses that cause a wide variety of viral diseases. The most common type of viral disease is the common cold, which is caused by a viral infection of the upper respiratory tract (nose and throat). Other common viral diseases include: chickenpox, flu (influenza), herpes, human immunodeficiency virus (HIV/AIDS), human papillomavirus (HPV), infectious mononucleosis, mumps, measles and rubella, shingles, viral gastroenteritis (stomach flu), viral hepatitis, viral meningitis and viral pneumonia.

Viral diseases are contagious and spread from person to person when a virus enters the body and begins to multiply. Common ways that viruses spread from person to person include:
Breathing in airborne droplets contaminated with a virus
Eating food or drinking water contaminated with a virus
Having sexual contact with a person who is infected with a sexually transmitted virus
Indirect transmission from person to person by a virus host, such as a mosquito, tick or field mouse
Touching surfaces or body fluids contaminated with a virus

Viral diseases result in a wide variety of symptoms that vary in character and severity depending on the type of viral infection and other factors, including the person's age and overall health. Common symptoms of viral diseases include flu-like symptoms and malaise.

Viral diseases are not treatable with antibiotics, which can only cure bacterial diseases and infections. However, the most common viral diseases, the common cold and the flu, are self-limiting in generally healthy people. This means that the viral infection causes illness for a period of time, then it resolves and symptoms disappear as the immune system attacks the virus and the body recovers.

In some cases, viral diseases can lead to serious, possibly life-threatening complications, such as dehydration, bacterial pneumonia and other secondary bacterial infections. People at risk for complications include those who have a chronic disease or a suppressed or compromised immune system, and the very young and very old. In addition, certain types of sexually transmitted viral infections, such as HIV/AIDS and HPV, can lead to serious complications and death. Seek prompt medical care if you think you have a viral disease, especially if you are at risk for complications, or if you believe you have been exposed to a sexually transmitted disease.

Seek immediate medical care if you, or someone you are with, have serious symptoms of an illness or a viral disease, such as shortness of breath, chest pain, passing out (fainting), or a change in alertness or consciousness.

Symptoms of viral diseases
Symptoms of viral diseases vary depending on the specific type of virus causing infection, the area of the body that is infected, the age and health history of the patient, and other factors. Symptoms can include:
Flu-like symptoms (fatigue, fever, sore throat, headache, cough, aches and pains)
Gastrointestinal disturbances, such as diarrhoea, nausea and vomiting
Irritability
Malaise (general ill feeling)
Rash
Sneezing
Stuffy nose, nasal congestion, runny nose or postnasal drip
Swollen lymph nodes
Swollen tonsils
Unexplained weight loss

In infants, signs of a viral disease can also include bulging of the soft spot on the top of the head, difficulty with feeding, excessive crying or fussiness, and excessive sleepiness.

Serious symptoms that might indicate a life-threatening condition
In some cases, viral diseases can result in serious complications, such as dehydration or pneumonia. Seek immediate medical care (call 911) if you, or someone you are with, have any of the following symptoms: change in alertness or level of consciousness; chest pain; deep, wet chest cough that produces yellow, green or brownish phlegm; high fever (higher than 101 degrees Fahrenheit); lethargy or unresponsiveness; seizure; shortness of breath, wheezing or difficulty breathing; stiff neck; yellowing of the skin and whites of the eyes (jaundice).

What causes viral diseases?
Viral infections occur when a virus enters the body and invades the inside of the body's cells in order to reproduce. If the body's immune system is unable to fight off the virus, it multiplies and spreads to other cells, repeating the process and leading to a widespread infection.

Types of viruses
There are more than 200 different viruses that can cause a cold or an upper respiratory infection. Other common viruses include:
Epstein-Barr virus causes infectious mononucleosis (cytomegalovirus causes a very similar disease in some people).
Human immunodeficiency virus (HIV) causes AIDS.
Human papillomaviruses (HPV) cause HPV infection, cervical dysplasia, genital warts and cervical cancer.
Influenza viruses, such as H1N1, cause influenza (flu).
Respiratory syncytial virus (RSV) causes lower respiratory tract infections in young children.
Rhinoviruses cause the common cold.
Rotavirus, enteroviruses and noroviruses cause viral gastroenteritis.
Varicella zoster virus causes shingles and chickenpox.
West Nile virus causes West Nile fever.

Ways to become infected with a virus
A person can be infected with a virus in a variety of ways, including:
Being bitten by an animal infected with a virus
Being bitten by an insect infected with a virus, such as West Nile virus
Breathing in airborne droplets contaminated with a virus
Eating food or drinking water contaminated with a virus
Having sexual contact with a person who is infected with a sexually transmitted virus
Sharing needles for tattooing or drug use with an infected person
Touching infected faeces or body fluids and not washing your hands before eating or touching your mouth, eyes or nose
Touching surfaces contaminated with a virus
Transmission of a virus from an infected mother to her baby during pregnancy or delivery

[Figure: Overview of viral infections, a chart listing viruses by the part of the body they affect. Encephalitis/meningitis: JC virus, Measles, LCM virus, Arboviruses, Rabies. Pharyngitis: Adenovirus, Epstein-Barr virus, Cytomegalovirus. Cardiovascular: Coxsackie B virus. Hepatitis: Hepatitis viruses A, B, C, D and E. Skin infections: Varicella zoster virus, Smallpox, Molluscum contagiosum, Human papillomavirus, Parvovirus B19, Rubella, Measles, Coxsackie A virus. Gingivostomatitis: Herpes simplex virus type 1. Parotitis: Mumps virus. Eye infections: Herpes simplex virus, Adenovirus, Cytomegalovirus. Pneumonia: Influenza virus types A and B, Parainfluenza virus, Respiratory syncytial virus, Adenovirus, SARS coronavirus. Myelitis: Poliovirus, HTLV-I. Gastroenteritis: Adenovirus, Rotavirus, Norovirus, Astrovirus, Coxsackie B virus. Pancreatitis: Coxsackie B virus. Sexually transmitted diseases: Herpes simplex virus type 2, Human papillomavirus, HIV]

Risk factors for viral diseases
Viral diseases can occur in any age group or population. Everybody contracts viral diseases during their life, although in some cases the virus does not cause obvious symptoms. Risk factors for catching a viral disease or developing complications include: advanced age; a compromised immune system due to an immunodeficiency disorder, HIV/AIDS, cancer or cancer treatment, kidney disease or other condition; a history of chronic disease, such as asthma, COPD, diabetes, tuberculosis or heart disease; malnourishment; not getting enough rest and having high levels of stress; not washing hands frequently, especially before eating, after using the restroom, or after touching common surfaces; sharing needles to inject drugs or for tattooing; unprotected sex with a partner who has had one or more other sexual partners; young age, including infancy and elementary-school-age children.

Reducing the risk of viral diseases
We can lower the risk of catching or spreading a viral disease by:
Abstaining from sexual activity, or only engaging in sexual activity within a mutually monogamous relationship in which neither partner is infected with a sexually transmitted disease
Avoiding contact of hands with the eyes, nose and mouth, which can transmit a virus into the body
Avoiding contact with a person who has a viral disease
Covering the mouth and nose with the elbow (not the hand) or a tissue when sneezing or coughing
Eating a well-balanced diet that includes sufficient amounts of fruits and vegetables
Getting sufficient rest
Using a new condom for each sex act
Using a sterile, unused needle for each act of tattooing or injectable drug use
Using appropriate antibacterial cleaners to clean hands and surfaces
Vaccination as recommended by the health care provider for viral diseases, such as chickenpox, shingles, influenza, HPV, hepatitis A and B, measles and mumps
Washing hands with soap and water for at least 15 seconds after contact with a person who has a viral disease, before eating, after using the restroom, or after touching faeces, body fluids, surfaces or foods that may be contaminated with viruses

Treatment of viral diseases
Treatment of viral infections varies depending on the specific virus and other factors. General treatment measures aim at relieving symptoms so that the person can get the rest needed to keep up strength and recover without developing complications. General treatments include: acetaminophen (Tylenol) or ibuprofen (Motrin, Advil) for fever, body aches and pain; drinking extra fluids; getting extra rest and sleep; maintaining good nutrition.

Depending on the type of viral infection and the presence of complications, other treatments may be needed. For example, a human papillomavirus (HPV) infection that leads to cervical dysplasia can be treated by surgical removal of the abnormal cells on a woman's cervix. Children younger than six should generally not use cold or cough medicines because of the risk of serious side effects. People with a viral disease should not use aspirin or products containing aspirin because of the risk of developing a rare but life-threatening condition called Reye syndrome, which has been linked to taking aspirin during a viral illness such as a cold or the flu.

Prescription medicines used to treat viral diseases
Antiretroviral medications help people with HIV/AIDS lead longer lives. They hinder the ability of HIV to reproduce, which slows the spread of HIV in the body.
Antiviral drugs minimise the severity and length of some viral infections, such as the flu and shingles, especially in people who are at high risk for serious complications. For example, the drugs oseltamivir (brand name Tamiflu) and zanamivir (brand name Relenza) may be prescribed for some cases of flu. These drugs are not appropriate for all people with the flu.
Antibiotics are not prescribed for viral diseases because they are ineffective against viral infections. They may be prescribed if a person with a viral disease develops a secondary bacterial infection, such as bacterial pneumonia, bacterial bronchitis or encephalitis.

Complementary treatments
Complementary and traditional treatments will not cure a viral disease, but may help to increase comfort, promote rest and minimise symptoms. Some possible treatments include: chicken soup to help break up congestion and provide easy-to-digest nutrients and extra fluids; supplements or products that contain vitamin C, echinacea or zinc; using a vaporizer; using mentholated ointments on the chest.

Possible complications of viral diseases
In some people, viral diseases can break down the body's defences and lead to more serious infections and life-threatening complications. It is therefore important to visit a health care provider when there are symptoms of a viral infection. Complications include: acute bronchitis; cervical cancer (from HPV infection); dehydration; frequent life-threatening opportunistic infections; otitis media (ear infection); pneumonia; secondary bacterial infection; seizures; shock and coma; sinusitis; worsening of asthma.

BACTERIA

Bacteria are single-celled microorganisms. They come in many shapes, including ball-, rod- and spiral-shaped. Most bacteria are not harmful and some are actually beneficial. Less than one per cent of bacteria will actually make you ill. Infectious bacteria can grow, divide and spread in the body, leading to infectious disease. Some infectious bacteria give off toxins which can make some diseases more severe.

Bacteria are spread in many ways:
Spread by aerosols (through coughing and sneezing), for example Streptococcus.
Spread by surface and skin contact, for example Staphylococcus aureus, including MRSA.
Spread through body fluids, such as blood and saliva, for example meningococcal disease (meningitis).

Antibiotics are usually given to treat severe bacterial infections. Antibiotic resistance in bacteria is a significant problem.

[Figure: Bacterial diseases, with the diseases Typhoid, Leprosy, Plague, Tetanus, Anthrax, Tuberculosis, Whooping cough, Diphtheria, Pneumonia, Diarrhoeal diseases and Cholera arranged around the centre label Bacterial Diseases]

TYPHOID (ENTERIC FEVER)
Typhoid is a common bacterial disease caused by a rod-like bacterium, Salmonella typhi, which is commonly found in the intestine of man. Certain humans function as carriers without suffering from it. Mary Mallon, called Typhoid Mary, was such a case. She was a cook and typhoid carrier who continued to spread the disease for several years through her food preparation.

Mode of transmission of typhoid
Incubation period varies from 1-3 weeks, average 2 weeks.
Typhoid spreads through food and water contaminated with faeces of the patient. House flies may carry the pathogens from the faeces to food, milk and water.

Symptoms of typhoid
This disease is characterised by inflammation of the ileum and colon. The liver and spleen also become enlarged. Symptoms include abdominal pain, pea-soup diarrhoea which may become haemorrhagic, constant fever, extreme weakness, vomiting, a rash of rose-coloured spots called rose spots on the upper abdomen, and sore throat. Typhoid is diagnosed by the Widal test.

Prevention and treatment of typhoid
Any patient with typhoid requires the highest standards of nursing, together with isolation and hygienic disposal of faeces.
The two most important preventive measures are proper sewage treatment and purification of water supplies.
Contamination of food can be reduced by personal hygiene and control of flies.
TAB vaccine provides immunity for about 3 years.
Antibiotics like ampicillin and chloramphenicol are used to treat typhoid.

CHOLERA
Cholera, commonly called haiza, is a water-borne disease caused by the bacterium Vibrio cholerae. Robert Koch discovered this disease.

Mode of transmission of cholera
Incubation period varies from a few hours to 2-3 days. It spreads through contaminated food and drinks. The causative bacterium secretes cholera toxin, an enterotoxin which induces excessive secretion of an isotonic electrolyte solution by the intestinal mucosa. This solution is lost in stools.

Symptoms of cholera
Cholera is mainly characterised by sudden onset of profuse, effortless, rice-water-like stools, vomiting and rapid dehydration, loss of minerals and muscular cramps.

Prevention and treatment of cholera
Proper sanitation and hygienic conditions are the best methods of prevention. Cholera vaccine is effective for six months only.
Fluid and salt lost is restored by Oral Rehydration Solution (ORS), which is water with a small amount of sugar and salt.
Antibiotics like tetracycline and chloramphenicol are used to treat cholera.

DIARRHOEAL DISEASES
Diarrhoeal diseases are a group of diseases caused by different bacteria such as Shigella dysenteriae, Escherichia coli, Campylobacter, Salmonella and Clostridium.

Mode of transmission of diarrhoeal diseases
Incubation period is variable. Epidemics are common in overcrowded, insanitary conditions. It spreads through food poisoning, contaminated food, water or drinks, clothes, utensils and bed sheets.

Symptoms of diarrhoeal diseases
This is characterised by mild diarrhoea, that is, loose stools, if infected by E. coli, and frequent stools with blood and mucus and abdominal cramps if infected by Shigella. Other symptoms are dehydration, diminished appetite, fever, low blood pressure, and an increase in pulse rate.

Prevention and treatment of diarrhoeal diseases
One should avoid contaminated food and water. ORS is given repeatedly to check dehydration and loss of minerals.

PNEUMONIA
Pneumonia is a serious disease of the lungs characterised by accumulation of mucus or fluid in the alveoli and bronchioles to the extent that breathing becomes difficult. It is caused by Streptococcus pneumoniae or Diplococcus pneumoniae, and Haemophilus influenzae.

Mode of transmission of pneumonia
Incubation period is 1-3 days. A healthy person acquires the infection by inhaling droplets or aerosols released by an infected person, or by sharing glasses and utensils with an infected person.

Symptoms of pneumonia
The onset of pneumonia is usually sudden, with a single shaking chill, followed by fever, pain with breathing on the side of the lung involved, increased pulse and respiratory rates, and cough. In severe cases the lips and fingernails turn grey to bluish in colour.

Prevention and treatment of pneumonia
The patients should be isolated and healthy persons should not share their belongings. Pneumococcal conjugate vaccine (PCV13) is available. Drugs against pneumonia are erythromycin, tetracycline and sulphonamide. If untreated, pneumonia leads to death.

DIPHTHERIA
Diphtheria is an acute infectious disease in children, mostly characterised by the development of a grey adherent false membrane over the upper respiratory tract or throat. It is caused by toxigenic strains of Corynebacterium diphtheriae (rod-shaped, Gram-positive bacterium).

Mode of transmission of diphtheria
Incubation period is 2-5 days. The toxin produced by the pathogen causes nasal diphtheria, pharyngeal diphtheria and laryngotracheal diphtheria. The germs are present in the discharges from the nose and throat of patients and of healthy people who act as "carriers". The patients and carriers spread the disease through kissing, talking, coughing and sneezing.

Symptoms of diphtheria
Symptoms are fever, sore throat, sometimes vomiting, headache, epithelial necrosis caused by the toxin, and oozing of semisolid material in the throat which develops into a grey, false but tough membrane. The membrane chokes the air passage. Sometimes the bacterium infects the heart, nerve cells and adrenal glands. In severe cases, the respiratory tract is blocked, causing difficulty in breathing and even death due to choking. The 'Schick test' tests the presence of antitoxin and the state of hypersensitivity to diphtheria toxin.

Prevention and treatment of diphtheria
One should avoid close contact with the patient. DPT (diphtheria, pertussis and tetanus) vaccine is available. Erythromycin is used to treat diphtheria.

WHOOPING COUGH (PERTUSSIS)
Whooping cough is caused by Bordetella pertussis and is a common childhood disease affecting the respiratory system. It has an incubation period of 10-16 days and spreads by droplet infection or by direct contact.

Symptoms of whooping cough (pertussis)
It causes loss of appetite, fever, running nose, fatigue, sneezing and constant cough, leaving the child breathless, tired and red in the face. Later the voice becomes hoarse and the cough gives a whoop or a loud crowing sound while inhaling. The child usually vomits, and there is frothy discharge from the mouth and nose. Other complications may include vomiting, convulsions and pneumonia.

Prevention and treatment of whooping cough
Infants are immunised with DPT vaccination at six weeks, three months and five months. Erythromycin antibiotic is used for treatment.

TUBERCULOSIS
Tuberculosis (TB), also called Koch's disease, is caused by the rod-shaped, Gram-positive bacterium Mycobacterium tuberculosis. The bacterium releases a toxin, tuberculin, which destroys the organs it infects. It can affect almost any tissue or organ in the body, like the lungs, lymph nodes, brain, bones and joints, but disease of the lung is by far the most frequent.

Mode of transmission of tuberculosis
Incubation period is 3 to 6 weeks, or may be years. It spreads through sneezing, coughing, contaminated food and water.

Symptoms of tuberculosis
Constant cough and, in severe cases, sputum with blood, pain in the chest while coughing, loss of body weight, failure of appetite and a slight rise of temperature in the evening are the symptoms of lung TB. Sputum, tuberculin, X-ray and gastric analysis are carried out to diagnose tuberculosis. The tuberculin test is also called the Mantoux test.

Prevention and treatment of tuberculosis
BCG (Bacillus Calmette-Guerin) vaccine for TB was obtained from bovine bacillus by Calmette and Guerin in 1921. Before giving vaccination to any individual, it is important to check whether they are already suffering from TB or have recovered from it. The test is to puncture the skin with a special instrument which has a ring of six short needles (the Heaf test). This introduces tuberculin, purified from dead tubercle bacilli. In the absence of past or present TB, the skin shows no reaction. If an individual has the disease or has recovered, the skin swells and reddens at the injection site. This indicates substantial immunity, and no vaccine is offered.
Some of the anti-tuberculosis drugs are streptomycin, rifampicin, isoniazid, thiacetazone, PAS (para-amino salicylic acid), etc.
Direct observation treatment (DOT) is a programme under WHO for treatment of TB across the world.

ANTHRAX (BIOWAR DISEASE)
Anthrax is an acute infectious disease caused by an airborne, spore-forming, rod-like, non-motile bacterium, Bacillus anthracis. Bacillus anthracis can be easily grown in the laboratory. Anthrax spores can be produced in a dry form which can be stored as particles. These particles can be used in biological warfare. Spores are infective in dry form, not in wet form. It most commonly occurs in wild and domestic vertebrates (cattle, sheep, goats, camels, antelopes and other herbivores), but it can also occur in humans when they are exposed to infected animals or tissues from infected animals.

Mode of transmission of anthrax (biowar disease)
Infected animals shed large numbers of bacilli in the discharges from the mouth, nose and rectum, which sporulate in the soil. These spores are a source of infection. It requires thousands of spores to cause human infection. Anthrax does not spread from human to human.

Types of anthrax (biowar disease)
Anthrax infection can occur in three different forms: cutaneous (skin), gastrointestinal (by ingestion) and pulmonary (by inhalation).
(i) Cutaneous anthrax occurs when bacteria enter through skin cuts and wounds. A skin lesion begins as a papule and soon becomes a vesicle, which breaks and discharges bloody serum. This vesicle, in about 36 hours, becomes a bluish-black necrotic mass (dead tissue). It consists of minute particles rich in spores.
(ii) Gastrointestinal anthrax is caused by eating under-cooked meat of infected animals. The patient experiences chill, high fever, body aches, nausea, vomiting, bloody diarrhoea, loss of appetite, and frequent haemorrhages from the mucous membranes and in the skin.
(iii) Pulmonary anthrax is acquired by inhaling dust containing B. anthracis. Pulmonary anthrax is often called wool-sorter's disease.

Symptoms of anthrax (biowar disease)
Initial symptoms resemble those of a common cold. Later there is difficulty in breathing, cough, fever, fast pulse and cardiovascular collapse. If left untreated, anthrax in all forms can lead to septicaemia and death. Death is apparently due to oxygen depletion, secondary shock, increased vascular permeability, respiratory failure and cardiac failure.

Prevention and treatment of anthrax (biowar disease)
The only known effective prevention against anthrax is the anthrax vaccine, developed from an attenuated strain of B. anthracis. A suitable antibiotic like ciprofloxacin is quite effective, particularly if used in the initial stages of the disease. But in cattle, ciprofloxacin may be effective only in chronic area. Antibiotics should be given to unvaccinated individuals exposed to pulmonary anthrax. Penicillin, tetracycline and fluoroquinolones are effective if administered before the onset of lymphatic spread or septicaemia.

TETANUS (LOCK JAW)
Lock jaw disease is caused by the spores of Clostridium tetani that enter through wounds.

Mode of transmission of tetanus
Incubation period is 3-25 days, during which the bacterium secretes a powerful exotoxin, tetanospasmin, into the tissue. Blood carries it to the central nervous system and brings about tetanus of the muscles. Infection is acquired by contamination of wounds with tetanus spores, as these spores are abundant in soil manured with animal dung. Spores may survive for 60 or more years in contaminated soil.

Symptoms of tetanus (lock jaw)
Symptoms include painful muscular spasms, especially of the neck and jaw. The lock jaw condition occurs when the patient cannot open the mouth. Convulsions and paralysis of muscles, difficulty in chewing and swallowing, fever and headache are other symptoms.

Prevention and treatment of tetanus
All wounds should be treated carefully and cleaned with iodine solution. Immunisation of infants by DPT should be done. ATS (anti-tetanus serum) injection within 24 hours of injury provides passive immunity, while TT (tetanus toxoid) gives active immunity.

PLAGUE (BLACK DEATH)
Plague is caused by a rod-shaped, non-motile bacterium called Pasteurella (Yersinia) pestis and is transmitted by the bite of an infected rat flea, Xenopsylla cheopis. The first authenticated plague epidemics in India in modern times occurred in 1895-96, and from 1898 onwards the disease was appreciably manifest, reaching a peak in the year 1907. Pasteurella pestis is an endoparasite of the gut of the rat flea, which is an ectoparasite of rats and mice. Head louse (Pediculus) and bedbug (Cimex) may also transmit the germs from man to man.

Prevention and treatment of plague (black death)
Plague is confirmed by the Wayson stain test. Anti-plague vaccine, spraying of insecticides, killing of rats, nose caps and high cots (a rat flea can jump up to 45 cm) are some preventive measures. Streptomycin or oral tetracycline is effective against plague.

LEPROSY (HANSEN'S DISEASE)
Leprosy is a contagious chronic bacterial disease caused by Mycobacterium leprae, which is characterised by chronic infection of the skin and other tissues.

Mode of transmission of leprosy (Hansen's disease)
The incubation period is very long and averages 2-5 years. Infection occurs by prolonged contact with leprosy patients. The bacilli leave the body in nasal discharge, from the throat during coughing, sneezing and even speaking, and through broken skin lesions.

Symptoms of leprosy (Hansen's disease)
These include the appearance of light-coloured patches on the skin, thickening of the nerves, and partial or total loss of sensation in the affected parts of the body. These are accompanied by fever, pain, ulcers and skin eruptions. Deformities of toes and fingers may also develop. The lepromin test is used to evaluate leprosy using an intradermal injection of lepromin. Tuberculoid leprosy gives a positive test with lepromin, while lepromatous leprosy is negative to the lepromin test.

Prevention and treatment of leprosy (Hansen's disease)
No vaccine is available. Leprosy is treated with drugs like rifampicin, dapsone and clofazimine.

FUNGI
Fungi are microorganisms characterised by cell walls made from a substance called chitin. Most fungi are harmless to humans and some are edible. Other fungi can be infectious and may lead to life-threatening diseases. Fungi reproduce by releasing spores that can be picked up by direct contact or even inhaled. Fungal infections often affect the lungs, skin or nails. Some infections may also penetrate the body to affect organs and cause whole-body infections.

Examples of fungal infections include:
Athlete's foot: itching, scaling or cracking of the skin
Ringworm: reddish, itchy, scaly rash usually on the skin and scalp
Thrush: caused by the fungus Candida albicans, which can infect the mouth, vagina, stomach and urinary tract

Fungi that commonly cause skin diseases are called dermatophytes. "Dermatophytes" does not refer to a particular group of fungi, but rather to the fact that they attack the dermis, or skin. Fungal infections of the skin can be treated with topical creams as well as prescription drugs.

Athlete's foot
The best-known fungal skin infection is athlete's foot. It infects approximately 10 percent of the United States population. It is most common among adolescents and adults, but it may affect people of any age. Athlete's foot can grow on the feet in different forms:
Interdigital: Infection occurs between the toes, with scaling, fissuring or softened skin.
Moccasin: The fungi grow as a thick scaling over the entire sole of the foot (like a moccasin) and cause discomfort.
Vesicular: The fungi appear as small, itchy blisters near the instep.
Ulcerative: The infection involves peeling, oozing discharge and a strong odour, and usually starts as red, itchy swelling between the toes.

A good way to combat athlete's foot is to keep feet clean and dry. Topical powders or creams may also help to control infection. Athlete's foot is tough to eliminate and often comes back.

Scalp itch
Scalp itch is a fungal infection of the scalp and hair. It usually occurs in young children, but may appear in all age groups. It is contagious and may be spread from child to child in a school or day care setting. An antifungal drug called griseofulvin cures scalp itch in one to three months.

Nail fungus
Nail fungus is most common in adolescents and adults, especially among people who have frequent manicures. These infections can show themselves in a variety of patterns. Sometimes a portion of the nail becomes thick and brittle. Other times, the fungi attack the cuticle and the growth spreads out from there. This cuticle-based infection is common in AIDS patients.

PARASITES

A parasite is an organism that lives off another organism, typically attaching itself to feed from the victim's blood, bowels or other bodily fluids. Parasitic diseases are more common than most people realise, and can strike anyone regardless of race, age or social status. A certain number of parasites are normally found on the skin and bedding of every human being. Dust mites and other tiny, harmless mites are commonly found in all households. Harmful parasites, however, can cause a great deal of damage to the human body if not properly treated.

Parasitic diseases symptoms
Parasites such as roundworms feed off the human waste in the intestines. Symptoms of various worm infestations include itching, usually of the anus or vaginal area, weight loss, increased appetite, abdominal pain, bowel obstructions, vomiting, disturbed sleep, worms present in the stools or vomit, diarrhoea, anaemia, symptoms of pneumonia, food poisoning symptoms, aching muscles or joints, or a general feeling of illness. These symptoms can range from barely noticeable to very severe.

Parasitic diseases causes
Parasitic disease is typically caused by the parasite's entry into the body via the skin or mouth. It is not unusual to pick up parasitic infections from soil, typically by either walking barefoot and allowing entry through the feet, or by placing the hands in the dirt and eventually placing the fingers in the mouth. Often people carry a parasite without ever knowing it. Parasites such as lice are caught through human contact with a person who is infected with lice. Ticks can be picked up through walking outdoors, close contact with a dog or cat, or being brought in from outside in various packages. Mosquitoes are parasites which simply attack humans for their blood and leave as quickly as they came.

[Figure: Trypanosome life cycle in the tsetse fly and humans. Tsetse fly stages: (1) Tsetse fly takes a blood meal and injects metacyclic trypomastigotes; (8) epimastigotes multiply in the salivary gland and transform into metacyclic trypomastigotes; (7) procyclic trypomastigotes leave the midgut and transform into epimastigotes; (6) bloodstream trypomastigotes transform into procyclic trypomastigotes in the midgut, which multiply by binary fission; (5) tsetse fly takes a blood meal, ingesting bloodstream trypomastigotes. Human stages: (2) injected metacyclic trypomastigotes transform into bloodstream trypomastigotes, which are carried to other sites; (3) trypomastigotes multiply by binary fission in body fluids such as blood, lymph and spinal fluid; (4) trypomastigotes in blood. Key: Infective stage and Diagnostic stage]

Parasitic diseases risk factor
Risk factors for parasites include children who play outdoors in the dirt, close contact with pets, farming, gardening, outdoor activities that include walking near wooded areas, digging in the dirt, walking outside barefoot, being in close or sexual contact with someone who has specific parasites, or simply the act of walking from the car to the house. Parasites exist in the world and cannot be avoided simply by avoiding being outdoors. Parasites can be found in foods, especially undercooked or exotic foods.

Physicians typically do not screen for parasites without cause. Blood tests or faecal samples can determine parasites, but not all parasites. Pinworms require a nightly anal test, typically for three nights, where a sticky slide is placed on either side of the anus to pick up any eggs that have been laid. Analysing the slide under a microscope can determine the presence of pinworm.

The majority of parasitic diseases are not dangerous. However, extreme cases may cause weight loss, dehydration from chronic diarrhoea, symptoms which mimic pneumonia, anaemia, fatigue, Lyme disease from ticks, malaria from mosquitoes, or a host of uncomfortable bowel syndromes.

Parasitic diseases treatment
Treatment of parasitic disease is typically nothing. Most often there are no symptoms, or symptoms are so mild that there is no concern. Unless there are serious symptoms or the infestation is large enough to cause health problems, most parasitic diseases will clear up on their own. For serious symptomatic cases, medication can be given to kill the parasite or to relieve the symptoms caused by it. Pinworm discomfort can be handled with an anti-itch cream, while Lyme disease can only be treated by treating the symptoms. Medicines such as mebendazole, pyrantel pamoate and albendazole are effective in killing worm infestations.

When dealing with an infestation of worms or other parasites, self-care can be as simple as keeping clean. Frequent bathing, cleaning clothes and bed clothes, wearing clean underclothing to bed, and checking for parasites are the best ways to deal with a parasitic disease. Washing hands frequently, especially after outdoor activities, can help reduce the chances of a parasitic disease.

Parasitic diseases prevention
Coping with a parasitic disease can be stressful, more so when the patient believes that parasites come from being dirty. Parasites can be contracted regardless of the cleanliness of the home. While hand washing and overall cleanliness are positive ways to prevent parasitic infections and diseases, they in no way guarantee that parasites will not infect a family member.

[Figure: There are different types of pathogens. Bacteria are single-celled organisms that cause illness by destroying cells and releasing toxic chemicals (Ex: Food poisoning, MRSA). Viruses are genetic material surrounded by a protein coat that force host cells to make more viruses (Ex: Flu, Cold, HIV). Fungi can be multicellular or single-celled, take nutrients from host cells by piercing healthy cells, occur in warm and damp places (Ex: Athlete's foot). Protozoa are single-celled organisms that use host cells to complete their life cycles and take nutrients from the host cell (Ex: Malaria). Review: Parasite]

INFECTIOUS DISEASES CHART

The chart below lists common infectious diseases, how each is spread, the time between exposure and sickness, early signs, how long the child is infectious, and when the child should be kept out of kindergarten or school.

NON-INFECTIOUS DISEASES AND THEIR CAUSES (CONCEPT MAP)

[Figure: Zoom - Non-Infectious Diseases and Causes. Diseases are a kind of Non-Infectious Diseases, which are caused by five groups. Body parts wear out: Rheumatism, Heart attack, Epileptic fits, Stroke, Migraines, Cataract, Cancer. Entry of harmful things: Allergies, Asthma, Poisons, Snakebite, Smoking cough, Stomach ulcer, Alcoholism. Lack of something needed by body: Malnutrition, Pellagra, Anemia, Goiter, Liver Cirrhosis. Problems by birth: Crossed or wall-eyes, Harelip, Deformities, Epilepsy, Retarded children, Birthmarks. Problems in mind: Anxiety, Belief in hexes, Uncontrolled fear, Paranoia. Non-infectious diseases are prevented by Exercise and Nutrition]

NON-INFECTIOUS DISEASES: MIGRAINES, EPILEPTIC FITS AND CATARACT (CONCEPT MAP)

[Figure: Zoom - Non-Infectious Diseases: Migraines, Epileptic Fits, Cataract. Non-infectious diseases are caused by body parts wearing out and may be prevented by exercise, nutrition and vitamins. Cataract: symptom is a cloudy eye, with the lens making the pupil grey or white on shining light into it; it needs surgery. Epileptic fits: symptom is fits in an otherwise healthy person with unconsciousness, violent movements and rolled-back eyes; due to heredity, brain damage at birth, high fever in infancy or tapeworm cysts in the brain; controlled by medicine such as phenobarbital or diphenylhydantoin. Migraines: symptom is often a severe, throbbing, one-sided headache with blurring vision, strange spots of light, numbness of one hand or foot, often with vomiting. It is very painful but not dangerous. Remedy: lie down in a dark, quiet place and relax; take 2 aspirin tablets with a cup of strong coffee or black tea]

INTEXT QUESTIONS PAGE NO. 178

Q1. State any two conditions essential for good health.
Answer:
Good health of a person depends on
(i) social environment.
(ii) public cleanliness.
(iii) good economic conditions and earnings.
(iv) social equality and harmony.

Q2. State any two conditions essential for being free of disease.
Answer:
The conditions essential for being free of disease are:
(i) Taking good food (balanced diet).
(ii) Maintaining personal and public hygiene.

Q3. Are the answers to the above questions necessarily the same or different? Why?
Answer:
The answers are not the same all the time, because the meaning of health varies from person to person. For example, good health for a dancer may be being able to stretch the body into difficult but graceful positions. On the other hand, good health for a musician may mean having enough breathing capacity in the lungs to control the voice.

There is one similarity in both cases. If the conditions essential for good health are maintained, then there are no chances of getting a disease.

INTEXT QUESTIONS PAGE NO. 180

Q1. List any three reasons why you would think that you are sick and ought to see a doctor. If only one of these symptoms were present, would you still go to the doctor? Why or why not?
Answer: When there is a disease, its symptoms and signs appear. These symptoms may be headache, cough, loose motions, a wound with pus, etc. These symptoms indicate disease but do not tell what the disease is. So, it is advisable to go to the doctor to diagnose the disease on the basis of these symptoms. The doctor will get laboratory tests done, if required, for confirmation of a particular disease.

Q2. In which of the following case do you think the long-term effects on your health are likely to be most unpleasant?
If you get jaundice,
If you get lice,
If you get acne.
Why?

Answer: Lice and acne will not cause long-lasting effects on the body. But in the case of jaundice, there will be severe long-lasting effects. For example:
(i) High temperature, headache and joint pains.
(ii) Feeling of nausea and vomiting.
(iii) Initiating rashes.
The patient will suffer from poor health and will recover by taking complete bed rest for some time.

INTEXT QUESTIONS PAGE NO. 187

Q1. Why are we normally advised to take bland and nourishing food when we are sick?
Answer: In case of illness, the normal functions of the body get disturbed. So, nourishing food is required which is easily digestible and contains all the nutrients. Therefore, bland and nourishing food is advised during sickness.

Q2. What are the different means by which infectious diseases are spread?
Answer: Infectious diseases spread by different means. These are:
(i) Through air: An infected person, when sneezing or coughing, releases droplets containing germs. These droplets infect another healthy person through air, and the microbes enter a new body. Examples of such diseases are common cold, pneumonia and tuberculosis.
(ii) Through water: If the water source is polluted by the excreta of infectious persons having gut diseases, and this water is used by other people, they will be infected. For example, cholera, amoebiasis and hepatitis spread through water.
(iii) Through sexual contact: Some diseases like AIDS and syphilis are transmitted by sexual contact. AIDS virus can also spread through blood, infected syringes, from an infected mother to her baby during pregnancy, and through breast feeding.
(iv) Through vectors: Some animals act as intermediaries or vectors for particular diseases. Vectors carry diseases from an infected person to a healthy person. For example, a mosquito spreads the malaria-causing organism to humans while sucking their blood.

Q3. What precautions can you take in your school to reduce the incidence of infectious diseases?
Answer: To prevent the incidence of infectious diseases in school, the following precautions can be taken:
(i) Avoid contact with students suffering from airborne diseases like common cold, cough, eye infection, flu, etc.
(ii) Check the availability of clean drinking water in school.
(iii) Keep surroundings clean, so that vectors do not grow and multiply.
(iv) Start a childhood immunisation programme in schools.

Q4. What is immunisation?
Answer: Immunisation is the process of administering (injecting) a vaccine into a healthy person in order to develop immunity against a disease. Immunity means the ability of the body to recognise, destroy and eliminate external disease-causing agents. This immunisation through administering a vaccine is called vaccination. A vaccine contains disease-causing organisms in a diluted or weakened form, or in living or dead form. It prevents further infection by microbes from causing the disease. Diseases like smallpox, rabies, diphtheria, chicken pox, polio and hepatitis are controlled by vaccination. Smallpox has been eliminated from the world through a worldwide vaccination programme.

Q5. What are the immunisation programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?
Answer: The following immunisation programmes are available at the nearest health centre in our locality:
(i) Immunisation for infants: DPT, BCG, polio, measles and MMR.
(ii) For children: Typhoid, TT, DT, smallpox and TAB.
(iii) For pregnant women: TT and hepatitis B.

The diseases like typhoid, polio, measles and tetanus are the major health problems in our locality. To prevent these diseases, the government has initiated an expanded immunisation programme all over the country.

EXERCISE QUESTIONS PAGE NO. 188

Q1. How many times did you fall ill in the last one year? What were the illnesses?
(a) Think of one change you could make in your habits in order to avoid any of/most of the above illnesses.
(b) Think of one change you would wish for in your surroundings in order to avoid any of/most of the above illnesses.
Answer: I fell ill twice in the last one year. The first illness was diarrhoea and the second was dengue fever.
(a) The changes I made in my habits after suffering from these diseases, to protect myself in the near future, are:
(i) I will always drink clean, pure water and wash hands before eating anything.
(ii) I will live in clean surroundings where disease-spreading vectors cannot multiply, for example, mosquitoes.
(b) Pure drinking water should always be available. The intake of impure water is the main cause of many infectious diseases.

Q2. A doctor/nurse/health-worker is exposed to more sick people than others in the community. Find out how she/he avoids getting sick herself/himself.
Answer: A doctor, nurse or health worker takes the following precautions to avoid becoming sick:
(i) Wear masks while diagnosing mouth or chest infections.
(ii) Clean their hands and wear gloves even while doing minor surgeries.
(iii) Get immunisation against all the infectious diseases.
(iv) Take a balanced diet (rich in proteins especially) to strengthen the immune system.
(v) Dispose of blood samples, urine or stool, sputum, etc. carefully.

Q3. Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by your local authorities to bring down the incidence of these diseases.
Answer: A survey in the neighbourhood found the following three most common diseases:

Q4. A baby is not able to tell her/his caretakers that she/he is sick. What would help us to find out (a) that the baby is sick? (b) What is the sickness?
Answer:
(a) Symptoms to help in finding out that the baby is sick are:
(i) continuous crying
(ii) drooping of eyes
(iii) redness of eyes
(iv) high temperature of the body.
(b) Signs which help to indicate the sickness in a baby:
(i) Loose motions and stomach pain indicate diarrhoea.
(ii) High fever, headache, muscular pain, and feeling of shivering and cold indicate malaria.
(iii) Redness and persistent rubbing of eyes indicate eye flu.
(iv) Pale skin, yellow urine and yellowing of the eyes indicate jaundice.
(v) Doctors suggest laboratory tests if there is fever with no other symptoms, to find out the kind of sickness.

Q5. Under which of the following conditions is a person most likely to fall sick?
(a) When she is recovering from malaria.
(b) When she has recovered from malaria and is taking care of someone suffering from chicken pox.
(c) When she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken pox. Why?
Answer: In condition (c), a person is most likely to fall sick. The reasons are:
(a) Due to malaria, the body becomes weak and loses body fluids. If she takes a four-day fast, her recovery from malaria-related weakness will not occur, and she will become weaker.
(b) Her immune system is already weak due to malaria, and if she takes care of someone suffering from chicken pox, there is a high probability that she may also suffer from this disease.

Q6. Under which of the following conditions are you most likely to fall sick?
(a) When you are taking examinations.
(b) When you have travelled by bus and train for two days.
(c) When your friend is suffering from measles. Why?
Answer: In condition (c), the chances of falling sick are maximum. Measles is an infectious viral disease of young children which spreads through nasal or throat discharge. Being in contact with a friend suffering from measles can make you sick.