According to WHO, “health is a state of complete physical, mental and social well-being. Health is not just the absence of disease. There are two types of diseases: Infectious and non-infectious The infectious diseases include Malaria and T.B while the examples of non non-infectious diseases are Haemophilia, cancer, allergy and rheumatoid arthritis The diseases can be prevented various methods. Besides personal public health measures like proper disposal of waste, decontamination of drinking water, and control of vectors are required. Our immune system plays the major role in preventing these diseases. Immunity can be: Inborn or Acquired. Inborn immunity is a non-specific type of defense present in body since birth. Acquired immunity is pathogen specific and activated only when the body encounters the pathogen. It is mediated by two lymphocytes: B cells and T cells. The B cells secrete five classes of antibodies: IgM, IgA, IgG, IgD and IgE. The T cells provide cell-mediated immunity. The response of immune system to specific environmental substances (Allergen) is called allergy. Among other diseases, AIDS and cancer kill a large number of individuals worldwide. AIDS stands for Acquired Immune Deficiency Syndrome. It is caused by Human Immuno deficiency Virus or HIV. It is detected by ELISA and Western Blot tests. There is no cure for AIDS. Cancer is caused due the uncontrolled division of cells in a part of the body that usually results in malignant tumor. It can be detected by: Biopsy, X-rays, CT Scan, Magnetic Resonance Imaging. Cancer can be treated by Surgery, Radiotherapy, Chemotherapy and Immunotherapy Millions of people, including young adolescents, around the world are addicted to narcotics and alcohol. Addiction to drugs and alcohol occurs due to: Curiosity, Peer pressure, Family problems, Academic stress and, desire to enhance physical endurance. Addiction to drugs and alcohol can be prevented by Counseling a child and encouraging him to discuss his problems with parents and friends.

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