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CBSE - IX
Diseases
Diseases
Health is defined as a state of physical, mental and social well being. A disease is an unhealthy condition caused by microorganisms, improper diet or it may be inherited. Classification of diseases is based on prevalence, occurrence or spread and duration. Epidemics are outbreak diseases that attack many people at the same time and spread very quickly. Classification of diseases based on occurrence or spread includes Infectious and Non-Infectious Diseases. Infectious diseases spread from one person to another through air, water, food, physical contact and insects, hence also called communicable diseases. Non-Infectious Diseases such as blood pressure are caused by nutritional deficiencies, hence called non-communicable diseases. Classification of diseases based on duration includes acute and chronic diseases. Diseases that last for a short period are called acute diseases. Diseases that last for a lifetime are called chronic diseases.
Causes of diseases might be due to contaminated water, lack of good nourishment and genetic abnormalities. Bacteria, viruses, fungi, protozoa and worms that cause diseases are called infectious agents. Diseases caused by bacteria are typhoid, cholera, tuberculosis and anthrax. Diseases caused by viruses are common cold, influenza, dengue fever and AIDS. Diseases caused by fungi are commonly skin infections. Diseases caused by protozoa are Kala-Azar and Sleeping Sickness. Diseases caused by worms are intestinal infections and lymphatic infections like elephantiasis. Organ and Tissue specific Manifestations of microbes depends on the mode of entry of microbes. Acquired Immuno Deficiency Syndrome or AIDS is so called because the AIDS virus breaks down the body’s immune cells and organs that comprise the immune system.
