9th Class Science Why do we fall Ill? Health and Diseases

Health and Diseases

Category : 9th Class


Health and Diseases




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


  • Basic conditions required for good health include balanced diet, personal hygiene, clean food, water and air, exercise, no addictions and good economic conditions.


  • Health is influenced by genetic, environmental, economic status and psychological factors.


  • A sign of a disease is a change in the bodily function or structure that can be observed, e.g., rashes, swelling or glands, change in colour of the skin, etc.


  • Depending upon the duration of diseases, they are classified into acute and chronic diseases.


  • Acute diseases last for a short period of ti-me whereas chronic diseases last longer, sometimes even for a lifetime.


  • Diseases where microbes are the immediate causes are called infectious diseases (common cold) and those, which are mostly internal, are non-infectious diseases (cancer).


  • Infectious agents spread diseases through air, water, physical contact or vectors.


  • Infectious diseases are caused by viruses (influenza, AIDS, etc.), some of the bacteria (typhoid, anthrax, etc.), fungi (candidiosis, aspergillosis, etc.), protozoans (malaria, kala- azar, etc.).


  • An infectious disease that can be spread from one infected individual to another is called a communicable disease.


  • Animals which act as carriers for the spread of diseases are called vectors. Mosquitoes are the vectors for the spread of malaria.


  • The basic principle of prevention of infectious diseases is the availability of proper and sufficient food for everyone, public health and hygiene.


  • Human immune system recognizes the infectious microbes and responds to it with greater vigour when an individual is infected for the second time by the same microbe. This forms the basis for development of immunization.


  • Edward Jenner introduced vaccination against small pox in 1776.


  • Prevention of a disease is more desirable than its successful treatment. We need a strong immune system and balanced diet for the prevention of diseases.



Notes - Health and Diseases

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