The document discusses the concept of health, distinguishing between being 'healthy' and 'disease-free', and outlines the various causes of diseases, including environmental factors, infectious agents, and genetic disabilities. It categorizes diseases into acute, chronic, infectious, and non-infectious types, and explains how diseases spread through various means such as air, water, and vectors. Additionally, it touches on disease treatment methods and the importance of vaccination to develop long-term immunity against pathogens.

1. WHY DO WE FALL ILL ?
CLASS – 9

2. ‘Health’ is a state of being – well socially, mentally and physically.
The conditions essential for good health are :-
• Clean surroundings, good sewage, proper sanitation and Rainwater Disposals.
• Availability of clean drinking water
• Availability of adequate, nutritious food.
• Social Equality and Harmony.
WHAT IS HEALTH ?

3. HEALTHY VS. DISEASE – FREE
Being Healthy Being Disease – Free
It is a state of being – well to function properly
physically, mentally and socially.
It is a state in which there is no discomfort in any
part of the body.
It is determined by the individual as well as social
and environmental factors.
It is entirely up to the individual.
A healthy person will be free of disease. A disease-free person may or may not be healthy.
A healthy person is energetic and capable of
performing as needed.
A disease-free person's performance depends on
his or her nature and personal attitude.

4. DISEASE AND ITS CAUSES
Human Health gets negatively affected due to physiological malfunctioning, psychological reasons or
pathogenic organisms. The term ‘Disease’ means Discomfort.
Disease can also be defined as malfunctioning of the normal state of living organisms that disturbs or
modifies the performance of the vital functions.
The disease can be caused due to the following reasons –
• Environmental Factors (Climate and Industrial Hazards)
• Infective Agents (Virus, Fungi, Protozoan and Bacteria)
• Genetic Disabilities

5. The vital factors which cause diseases are :-
• External Factors – The disease causing external agents which enter the human body from outside are
referred to as External Factors. Diseases caused by External Factors: Night blindness, Malaria, Rabies,
Hepatitis, Dysentery, etc.
• Internal Factors – The disease causing factors which exist within the human body are called Internal
Factors. Diseases caused by Internal Factors: Cardiac Failure, Short – Sightedness, Kidney Failure,
Allergies, etc.
SOURCES OF DISEASE

6. Types of Diseases Causes of Diseases Examples
Physical Damage to body parts Leprosy, Bone Fracture
Infectious Invasion of the body by microbes Typhoid, Diarrhea, Malaria, AIDS,
Polio, Cholera, etc.
Deficiency Inadequate diet Anaemia, Beri – Beri, Goitre, etc.
Inherited Abnormal genes passed from
parents to the offspring
Cystic Fibrosis, Sick cell Anaemia,
Haemophilia, etc.
Mental Brain Damage or Psychological Depression, Paranoia
Social Social interactions with family and
friends
Unhealthy lifestyles, Smoking,
Alcoholism, etc.
COMMON HUMAN DISEASES

7. DEFICIENCY DISEASES
Deficient Nutrient Disease
Vitamin A Night – Blindness
Vitamin B1 Beri – Beri
Vitamin B2 Cheilosis
Vitamin B12 Pernicious Anaemia
Vitamin C Scurvy
Vitamin D Rickets
Vitamin K Bleeding Disease
Iron Microcytic Anaemia
Fluorine Dental Caries
Iodine Goitre

8. LEVELS OF IMMEDIATE CAUSES
The organism which enters our body and caused the disease is called
as an Immediate Causes.
These causes exists in various levels, which are :-
• First – Level Causes :- They are the main cause by which the
disease happen and we fall ill. Microbes which are responsible for
First – Level Causes are known as Pathogens.
• Second – Level Causes :- These causes either make a person prone
to catch a disease or create condition that promote susceptibility to a
disease. Malnutrition and Genetic Abnormalities are the Second –
Level Causes of disease.
• Third – Level Causes :- Factors such as Public Health Services such
as Improper Sanitation, Unhealthy Drinking Water and Poverty
constitutes the Third – Level Causes of the diseases.

9. ACUTE DISEASES
Acute Diseases refer to a medical condition that occurs suddenly and lasts for a shorter period of time.
There symptoms are clearly visible in the body.
Examples :- Common Cold, Influenza, Typhoid, Cholera, etc.

10. CHRONIC DISEASES
Chronic Disease refers to a medical condition which lasts for a long period of time and have long – term
effects on our body.
Examples :- Elephantiasis, Cardiovascular Disease, Arthritis, Cancer, Tuberculosis, etc.

11. INFECTIOUS DISEASES
Infectious Diseases are the diseases caused by various pathogenic microorganisms such as Virus,
Bacteria, Protozoan, Fungi, and other Parasites. They are also known as Communicable Disease. These
infectious diseases can be transmitted by Animals, Humans, Insects or Other Agents.
Examples are – Malaria, Rabies, Mumps, Influenza, Hepatitis – B, Polio, Dengue, Smallpox,
Elephantiasis, SARS, Measles, Common Cold, Cholera and Tuberculosis.

12. INFECTIOUS AGENTS
Organisms that can cause diseases are classified in a wide range of categories
like Viruses, Bacteria, Fungi, Protozoan and Worms.
• Disease caused by Virus are :- Common Cold, Influenza, Dengue Fever,
AIDS, etc.
• Disease caused by Bacteria are :- Cholera, Typhoid, Tuberculosis, Anthrax,
etc.
• Disease caused by Fungi are :- Ringworm, Athlete’s Foot, Skin Infections,
etc.
• Disease caused by Protozoan are :- Malaria, Kala – Azar, Dysentery,
Sleeping Sickness, etc.
• Disease caused by Worms are :- Intestinal worm infections, Elephantiasis,

13. Means of Spread of
Infectious Disease

14. MEANS OF SPREAD OF DISEASES
Infectious Diseases spread from one Infected Person to a Healthy Person by various
methods.
 Air Borne Disease :- Disease causing microbes are spread through air (Droplet Transmission).
Examples :- Common Cold, Pneumonia, Tuberculosis, etc.
 Water Borne Disease :- Disease causing microbes are spread through water (Unhealthy
Drinking Water). Examples :- Cholera, Diarrhoea, Polio, Meningitis, etc.
 Sexually-transmitted diseases :- Disease causing microbes transmitted by sexual
contact from one partner to another (Other than Casual Physical Disease). Examples :- Syphilis, AIDS,
etc.
 Vector Borne Disease :- Vectors are the animals which carry the infecting agents from a sick
person to another potential host. Examples are :- Female Anopheles Mosquito is the Vector of Malaria.

15. Spread of
Air Borne
Disease

16. Diseases that do not require the presence of an infectious agent to cause disease are called Non-
Infectious Diseases (also known as Non – Communicable Disease). They arise as a result of Internal
Imbalances in our body.
Examples are – Asthma, Allergies, Diabetes, Heart Diseases, Cancer, Arthritis, Epilepsy, Multiple
Sclerosis, Anorexia and Bulimia.
NON – INFECTIOUS DISEASES

17. Infectious Diseases Non – Infectious
Disease
Diseases that spread from one person to
another are called Infectious Diseases.
Diseases that do not spread from one
person to another are called Non-
Infectious Diseases.
They are caused by microbes called
Pathogens such as Bacteria, Protozoans,
Viruses, etc.
They are also caused by the Pathogens.
Transmission of diseases occurs through
Direct Contact, Air, Water, Food etc.
Transmission of diseases occurs from
Parent to Offspring (Hereditary Disease).
Community Hygiene can reduce the risk
and occurrence of Diseases.
Societal Hygiene is ineffective in reducing
the occurrence of diseases.
Example: Cholera, Malaria, Covid – 19 Example: Diabetes, Cancer, Allergies, etc.
INFECTIOUS VS.NON – INFECTIOUS DISEASE

18. SYMPTOMS OF A DISEASE
Symptoms indicate the presence of disease. They are a collective indication of a number of diseases in
a Particular Part or Organ.
Point of Entry and Infection of Microbe in Human Body
Our body is quite large in comparison to any type of microbe. So there are many possible areas within
our body where microbes may reside. Different species of microbes move to different parts of the body.
For Example: if the microbes enter from the air via the nose, they are likely to go to the lungs. This
happens in case of bacteria which cause Tuberculosis (T.B.) of lungs. If the microbes enter through the
mouth, they can stay in the lining of the gut as do Typhoid-causing bacteria. These microbes, can also
go to the liver, like the viruses that cause Jaundice (Hepatitis B).

19. PRINCIPLE OF TREATMENT
There are two ways to treatment of the disease.
• To Reduce the Effect of Disease :- We can provide Treatments that will reduce the
Symptoms. The symptoms are usually a result of Inflammation. For Example – We can take Medicines
that bring down Fever, Reduce Pain or Loose Motions. We can take Bed Rest so that we can conserve
our energy. This exercise will enable us to focus on the healing.
• To kill the Microbes :- Pathogenic Microbes can be killed by two common methods. One Way
is to use medicines that Kill Microbes. If that drug affects Host’s Metabolism, then our very purpose of
treatment will be defeated.
 Second Way is to Our Cells may make new substances by a Mechanism different from that used by a
Pathogenic Bacteria. Antibiotics is a drug that blocks the Bacterial Synthetic Pathways but does not
affect our own Cellular Pathways.

20. PREVENTION OF DISEASE
Following three limitations are Normally Confronted while treating a
Disease :
• Once someone gets a Disease, his or her body functions gets
Damaged and May Never Recover Completely.
• Treatment of a Disease takes time it means that if someone is
Suffering from a Disease, he is likely to be Bedridden for
sometime, even if he is given Proper Treatment.
• The Person suffering from a Disease can serve as the Medium for
Further Spread of Infection to other people.

21. VACCINATION
A Vaccine is an Antigen that is Injected or Swallowed. It causes the
development of Active Immunity in the patient. Small Quantities of
antigen introduced into the person’s body Stimulate, the
Production of Antibodies as if the body was infected by the
disease. This type of immunity is Long Term since the body
develop Memory Cells in the Natural Pathway.
When the Immune System first encounters an infectious microbe, it
responds against it and then remembers it specifically. So the next
time that particular microbe, or its close relatives enter the body,
the immune system responds with greater vigor. This eliminates
the infection even more quickly than the first occurrence of the
disease. This is the basis of the Principle of Vaccination.

22. PEPTIC ULCER
Peptic Ulcers are Painful Bleeding Areas within the Stomach and the
Duodenum. They were once considered to be caused by increased
Gastric Acidity due to Stress of the afflicted persons. Robin Warren
(born 1937) a Perth based Australian pathologist observed in 1984 that
areas of peptic ulcers contained many small curved gram negative
bacterium, named Helicobacter Pylori. Barry Marshall (born 1951), a
young clinical fellow of Warren succeeded in culturing the bacteria.
They found that Amoxicillin, an antibiotic effective in killing the bacteria
could also cure the Peptic Ulcers. The finding helped in changing once
painful chronic and disabling condition into a short duration treatable
disease. For this breakthrough Marshall and Warren were awarded
Nobel Prize for Physiology and Medicine in 2005.