Health is a state of complete physical, mental and social well being and not merely the absence of disease.
- The conditions necessary for good health are –
(i) Good physical and social environment.
(ii) Good economic conditions.
(iii) Social equality and harmony.
Thus, for maintaining good health, balanced diet, hygienic surroundings, proper habits, exercise and relaxation habits are necessary.
- Hygiene is the conditions or practices conducive to maintaining health and preventing disease, especially through cleanliness.
- Disease is any harmful change that interferes with the normal appearance, structure, or function of the body or any of its parts.
- Disease may be caused by infection like virus and bacteria, lack of good nourishment, genetic difference etc.
- Infectious diseases are caused by microbes or micro-organisms.
- Disease like cancer, high blood pressure etc. are non-infectious and do not spread from one person to another.
- Infectious diseases are caused by bacteria, viruses, fungi and unicellular animals like protozoans. Also, some multicellular organisms like worms may also cause infectious diseases.
- There are following main kinds of germs/pathogens (infectious agets) –
(i) Diseases caused by bacteria are sore throats, ear infections, pneumonia, typhoid fever, cholera, tuberculosis, anthrax etc.
(ii) Viruses cause common cold, influenza, dengue fever, AIDS, chicken pox, measles, flu etc.
(iii) Disease caused by fungi are athlete’s foot, common skin infections etc..
(iv) Diseases caused by protozoa are malaria, amoebic dysentery, kala-azar etc.
(v) Worms cause intestinal diseases as well as elephantiasis.
- The diseases that last for short periods only are called acute diseases, e.g. common cold.
- The diseases that last for very long periods, sometimes even for lifetime, are called chronic diseases, e.g. elephantiasis.
- On the basis of period of occurrences, diseases may be either congenital, i.e. inborn diseases ordiseases right from the birth, e.g. haemophilia, and acquired, i.e. acquired during the lifetime.
- Acquired diseases are two types-communicable diseases (which can be transmitted from an infected to a healthy person, and non-communicable, which cannot be transmitted.
- Infectious agents spread through air, water, physical contact or vectors.
- The period between the entry of the organisms inside the body and the appearance of the symptoms of disease is called incubation period.
- The preventive inoculation against a disease is called vaccination.
- The system of the body which protects it from various infectious agents and cancer is called immune system.