Diseases Diseases

What Causes Diseases


The term 'disease' is described as a condition in which the normal functioning of the body gets disturbed. Many times such conditions are not very serious and get cured, but sometimes they become serious and even fatal. Disease is a departure from normal health through structural or functional disorder of the body.

Diseases can be categorized in several ways based on -

  1. Extent of occurrence - Endemic, epidemic, pandemic and sporadic
  2. Communicability - Whether infectious (caused due to germs) or non-infectious (due to body's own poor functioning).
  3. Kinds of pathogen - Whether bacterial, viral or some other types of germs
  4. Kinds of transmitting agent - Whether water borne, food borne, or insect borne etc.


What causes diseases? To understand this, diseases are classified into two major categories: non-communicable or non-infectious and communicable or infectious. 

1. Non-communicable or non-infectious diseases - In these diseases there is no germ of any kind and they cannot spread from a patient to another person by contact or by any other method i.e. they are non-transmissible. Examples - diabetes, color blindness, heart attack, beriberi etc.

2. Communicable or Infectious diseases - These are caused by some germs. The germs somehow must reach a new healthy person before he can suffer from the disease. The cause of the disease is called pathogen and its transmission from one person to another is called infection. An infectious disease usually does not appear immediately after the infection but it may take some time varying from a few hours to a few days, this period is called the incubation period. Common examples: cholera, smallpox, malaria etc.


Here is a simplified classification of the cause of non-infectious diseases with some common examples. 

  1. Nutritional deficiency - Beri-beri, scurvy, goiter, night-blindness etc. 
  2. Metabolic - Sugar diabetes, goiter
  3. Genetic - Hemophilia, Thalassemia
  4. Allergies - Hay fever, asthma
  5. Degenerative - Arthritis, cataract
  6. Mental illness - Depression, schizophrenia
  7. Cancer - Breast cancer, prostate cancer, leukemia 
Many causes are suggested for cancer and this includes chemicals, tars from tobacco smoking, tobacco chewing, drugs, pollution, certain radiations and even certain viruses. The agent that causes cancer is called carcinogen. 
Infectious diseases on the other hand always occur due to some disease causing organism called pathogen. The pathogens include various kinds of plants as well as some small animals. Following is a list of some common pathogens and the diseases they produce. 
  1. Viruses - Common cold, influenza, mumps, polio, rabies, smallpox, measles, yellow fever, AIDS etc. 
  2. Rickettsiae - Tick fever, typhus fever
  3. Bacteria - Tuberculosis, cholera, tetanus, typhoid, gonorrhoea, syphilis, diphtheria, pneumonia etc. 
  4. Moulds and fungi - Ringworm, athlete's foot
  5. Protozoa - Malaria, amoebic dysentery, sleeping sickness etc.
  6. Worms - Filaria, guinea-worm, tape worm, sound worm, pinworm etc. 
  7. Mites - Scabies

Tips and comments

Early man looked at disease as an act of God or evil spirits. He used magical methods and sorcery for the treatment of the disease. Today science looks at every disease to be a condition which has a definite cause and thereby making it possible to prevent it or cure it. To make people conscious and aware of staying healthy and disease free World Health Day is celebrated on April 7th.

By Smita, published at 01/12/2012
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