Health is defined as a state of complete physical, mental and social well-being. (i) The factors which affect human health are: (a) Genetic disorders (b) Infections (c) Lifestyle. (ii) Balanced diet, personal hygiene and regular exercise are very important to maintain good health. (Hi) Awareness about diseases and their effect on different body functions, vaccination against infectious diseases, proper disposal of wastes, control of vectors, maintenance of hygienic food and water resources are necessary for achieving good health. 2. Disease is a state when functioning of one or more organs or systems of the body is adversely affected, characterised by various signs and symptoms. Diseases can be divided broadly into the following two categories depending on the modes of transmission I. Infectious diseases which easily transmit from one person to another, e.g. AIDS, common cold, etc. II. Non-infectious diseases which does not transmit from one person to another, e.g. cancer, diabetes,