The term ‘disease’ is a broad term. There are more than thousand diseases each of different nature affecting people of different ages and affecting different parts and organs of the body. Many odd diseases have been reported including the Gulf-war Syndrome, the Nodding disease and the Exploding Head Syndrome. Some diseases have no known cure such as the well known autism and the famous HIV. In some cases, even the causes of certain odd diseases have not been found out and are only assumed.
Diseases and conditions can be broadly classified into infectious, environmental and prenatal diseases, though some diseases overlap within these categories. Some conditions are experienced after an injury and accident. They can be classified under environmental diseases.
Infectious diseases are illnesses where pathological agents like bacteria, virus and fungi affect the person. The affected person is generally termed as the ‘carrier’ and he in turn transmits to another healthy person and it spreads on. The common transmission types of the diseases are touching, sneezing, coughing, and kissing while there are certain diseases which are transferred sexually like the HIV and through other external carriers called as the ‘formites’ which is an inanimate object like a coin that is infected with pathogens or a glass used by the infected person. Other external carriers are the ‘vectors’ which are bugs that have bitten the carrier of the disease.
Environmental diseases are caused by external factors such are adverse climatic conditions or malnutrition or by habits such as smoking or drinking and are not transmitted genetically or through infections. Exposure polluting elements and toxic gases causes many of the environmental diseases. Most of these diseases are obtained due to exposure to unsafe workplace such as the familiar asbestosis. Habits such as drinking or in-taking drugs cause depressions and other mood related disorders, which are also classified under environmental diseases. Nutritional diseases may be either due to malnutrition such as anemia, tetanus and scurvy or over-nutrition like obesity.
Genetically transferred diseases are transferred from the infected mother to the infant. Some of these diseases are caused by the complexion during the process of child birth of during the pregnancy period. The most famous of this kind of diseases are the autism and the cerebral palsy caused by complexions during the process of child birth.
Despite these diseases there are many other diseases and conditions which are not known of the nature, causes and origin. There are certain common precautions that are to be followed such as washing hands often and covering the nose and the mouth while sneezing or coughing to avoid the transfer of diseases.