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CLASS 9 Why do we fall ill?


 It is a state of well being physically,socially and mentally.

Significance of health:

  • Good health makes the person happy.
  • Health involves body, mind and social well being.
  • Regular exercise keeps us healthy.
  • Personal health.
  • Community health.
Personal Health:
It involves health of a person i.e. physical, mental and social well being of an individual.

Community Health:

It is overall well being of whole community means environment does not have pollution. People take healthy food.

Maintenance of community health:

  • Proper environment without pollution
  • Proper garbage disposal system and proper sanitation facilities
  • Proper drinking water
  • All people clean their body and surrounding

Difference between Healthy and Disease free:

Disease Free
It is a state of well being physically,socially and mentally. It is a state of absence of any diseases and all cells, tissues, organs work properly.
It includes individual along with physical and social environment, ex- old people who live alone have depression which spoils their health.If there is garbage near your house, all people living nearby will not be healthy. It refers to individual only, keeping body clean, taking proper diet, doing exercise regularly can make us disease free.


It is lack of ease i.e. a person is uncomfortable. If our body organs are not functioning properly. We are suffering from a diseases.

Types of disease:

  • Acute diseases: These are for short periods.Example - Common cold, cough, malaria, dengue, loose motions.
  • Chronic diseases: These diseases can last for long time, maybe for whole life. Example- diabetes, heart ailments, hypertension.These affect specific organs.
  • Infectious diseases :Those diseases which spread due to infection by micro-organisms and communicated or transmitted from one person to another through air, water, vectors like mosquito etc. Example- Tuberclosis,chicken pox, smallpox, conjunctivitis, AIDS.
  • Non- infectious diseases: The disease does not spread by contact through air, water. Example- Arthritis,heart ailments,diabetes,hypertension.
Causes of disease:
  • Micro-organism like bacteria, virus, fungi, Protozoan and worms.
  • Poor Nourishment and wrong eating habits.
  • Heredity and genetic disorder.
  • Lack of proper vaccination
  • Environmental pollution like air water
Disease causing organisms:

Virus: Virus cause common cold, influenza, dengue, fever, polio, hepatitis, AIDS, chicken pox, mumps, smallpox, swine flu

Protozoa: Leishmania causes Kala Azar, malaria, amoebic dysentery, sleeping sickness

Bacteria: Typhoid fever, Cholera, tuberculosis, Anthrax, food poisoning

Fungi: Skin diseases like athlete's foot, ring worm and other skin infections

Worm : Intestinal infections, elephantiasis

Means of spread:

Air: The microbes spread in air by sneezing and coughing like common cold, tuberculosis, pneumonia spread to a healthy person.

Water: The microbes enter our body by drinking polluted water and infected food. Example- Cholera, amoebic dysentery.

Vectors: Some organisms like female Anopheles, Mosquito act as a carrier of disease like Malaria, dengue, yellow fever

Through sexual contact: Sexually transmitted diseases like AIDS spread by sexual contact with infected person, blood transfusion from mother to child during pregnancy.

Rabid animals: Rabies is spread through the bite of animals. Bird flu and Swine Flu are caused by infected animals and birds.


The drugs which are obtained from microorganisms and are used to kill or suppress the multiplication of microorganism are called antibiotics. Example – penicillin,streptomycin,tetracycline

Immune system:

It is a defence mechanism of the body to fight against infection. Antibodies fight against antigens (causing diseases). WBC also protect from infections.

Principles of treatment:

There are two ways of treatment-
  • To reduce the effects of the diseases
  • To kill the cause of the disease
Reduce Symptoms: The symptoms are generally reduced after treatment.For example, if we take medicine to bring down fever, headaches, bodyache will disappear.

Killing of Microbes: Antibiotics are used to kill micro – organism.Chloroquin is used for treating malaria,this drug kills protozoa causing malaria.

Why Antiviral drugs are difficult to make?

Antiviral drugs are difficult to make because virus do not have their own biochemical mechanism and they use our mechanism for life processes.Common cold has no specific treatment.

Principles of prevention:

General ways

  • Public hygiene
  • Proper and sufficient food
  • No pollution of air and water
  • Proper garbage disposal system
  • Proper sanitation
  • Safe drinking water
  • No stagnant water
  • Mosquito repellent
  • Pest control
Specific ways

Immunization :

The process of introducing weak and pathogen inside the body of the host to fool immune system and to produce antibodies against infections from particular disease.

Question Bank

1.    Which micro - organism causes kala-azar?
2.    Why is aids considered to be a syndrome and not a disease?
3.    Which parameters of health are difficult to measure?
4.    Who discovered vaccine for the first time?
5.    What precautions will you take to justify “prevention is better than cure” ?
6.    State any two conditions essential for good health.
7.    What is an antibiotic ? Give its one example.
8.    What is meant by acute diseases?
9.    Write the full form of WHO ?
10.  Why is food necessary for us?
11.  Write the full form of AIDS.
12.  Name two STD (sexually transmitted diseases).
13.  Which organ is affected when a person is suffering from jaundice?
14.  Why is antibiotic not effective in common cold?
15.  Give two examples for each of the following
       (a) Acute diseases                                       (b)  Chronic diseases   
            (c)  Infectious diseases                                (d)  Non - Infectious diseases

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