Diseases are many and with time even more diseases come up.
There are many new diseases which appeared in recent century and scientists are busy in recognizing them and also giving suitable names.
Hence deadly diseases like AIDS, Hepatitis were not even know or heard in 19th century but now they are widespread.
Similarly some diseases have been eradicated from the world. But still the ratio of emergence of new ones and extinction of old ones has a large difference.
There are almost no diseases which are getting extinct due to change in lifestyle and health habits of man.
Among the diseases there are many kinds based on the causing agent or the changes in the body physiology.
Different types of diseases:
1) Infectious diseases: These are the diseases caused by an external organism.
This organism can be a microbe like bacteria, protozoa, fungi or even virus. Sometimes they can be caused by parasites like ascaris, nematodes which survive in the human body for years.
Infectious diseases are the sole type of diseases which threatened the humanity for centuries. They were so dangerous that they wiped out few cities and even countries of human population. They were very tough to control, but due to discovery of antibiotics, most of them are under control.
Examples: Tuberculosis, AIDS, plague, typhoid etc.
2) Genetic diseases: These are the diseases caused by a genetic change in the body. This usually occurs from birth due to incompatibility of chromosomes between parents. Sometimes these are caused due to defective the transfer from parents to children. Ex: Hemophilia,
3) Autoimmune diseases: Here the body produces anti-bodies to destroy its own cells. This is a bit strange condition in some people. Here the body immune system itself destroys a tissue or organ in the body leading to disease.
These diseases can be observed as idiosyncratic diseases. Ex: Type-I diabetes, rheumatism, systemic lupus erythematosus.
4) Physiological dysfunctions: This is a types of disease where in body physiology gets deranged. This derangement can be from external influence or some times from within. The disturbances in the physiology can be sometimes deadly unless normalized. Ex: Sunstroke, piles,acidity
5) Organ diseases: This is a disease mostly confined to a single organ. Due to change in life style, we are prone to excess use of some organs. On the other hand we are prone to lack of physical activity. This lack of activity leads to organ dysfunctions and disturbances. Ex: Heart problem, blood pressure, eye sight etc.
6) Trauma (injury): This is an injury to the whole body or part of the body. The injury can be due to external physical blow or a fall. Also it can be internal like brain and spinal cord injury due to lack of oxygen. This trauma can also be mental related. Ex: Post traumatic stress disorder, Asphyxia in new born babe etc.
7) Mood disorders (condition): These are the ones which are due to disturbance in thought and behavior. They are either organic i.e. due to damage to nerves or brain. Symptomatic i.e. there is no physical alteration in the brain but only the mood. Ex: Anxiety, depression, psychosis.
8) Chronic diseases: These are the long standing diseases. They stay for years till the death of the patient in most cases. They need regular treatment to keep up the normal life style. If not they can lead to disability and untimely death. That is they are not curable but one can only treat them. Ex: diabetes,blood pressure.
9) Acute diseases: These are very short standing diseases. They stay for few days to a week. They are curable ones.Ex: routine fever, head ache, cold.
10) Sub-acute diseases: These are the ones which stay for more than a week to 2 weeks. In most cases less than a month. Ex: sunstroke, typhoid etc.
11) Local diseases: These are the one which are restricted to some part of the body. They may or may not spread but do not harm remaining body. They are localized to one place in the body. Ex: gastric ulcer, mouth ulcer, piles etc.
12) Systemic: These are the diseases which affect whole of the body. They are spread in the whole body during the condition: Ex: anemia, blood cancer etc.
13) Progressive: These are the ones which increase in severity with time. Most of the times they go undiscovered in the initial phases. Then they become so severe that normal life gets hampered. Ex: cancer, chronic obstructive pulmonary disorder.
14) Refractory diseases: These are the ones which might turn up again with increased severity. They also will be less responsive to drugs. Ex: tuberculosis
15) Organic diseases: These are the one which are caused due to change in the body chemistry. This happens due to excess secretion of an hormone, accumulation of toxic waste or lack of enzymes. Ex: gout.
16) Life style related: These are the disease due to life style. Those who do not have proper life style and lead sedentary life will face them. These get cured with proper life style. Ex: irritable bowel syndrome, constipation etc.
17) Food born: These are acute diseases which arise due to food. Some of them allergic to certain foods like mush rooms,potato, curd etc. When they consume these food, they have some allergic reactions and even swellings in some part of the body. Even for many dairy products like curd cause cold.
18) Air borne: These are the diseases caused by air pollution. The common type of diseases are asthma, stuffy nose etc.
19) Water borne: These are the diseases which occur due to contaminated water. Many people suffer from loose motions, abdominal pain due to contaminated water. The water contains microbes like shigella, entamoeba (amebiasis) like microbes which cause the disease. Similarly cholera and typhoid are caused by drinking contaminated water.
20) Hospital borne: It is quite interesting that some people catch infections when they visit hospitals. They are so specific that these microbes infect those who stay in hospitals.Ex: nosocomial infection.
21) Nutrient deficiency diseases:These are the diseases caused due to deficiency of nutrients. Examples are kwasioskar, marasmus etc.
22) Vitamin deficiency diseases: These are the diseases caused due to vitamin deficiency. They can be cured by taking vitamin supplements. Ex: hemophilia due to lack of vitamin k.
Also there are different categories of diseases like viral, fungal etc based on the type of microbe causing it. Similarly there are different types of diseases based on the organ affected like eye, skin, heart etc. But alternative medicine systems like Ayurveda and homeopathy do not consider this classification of diseases.