There are many types of diseases. Human diseases can be broadly classified into two groups on the basis of their time of occurrence. They are
1. Congenital diseases and
2. Acquired diseases
1. Congenital diseases
• The congenital diseases are present since birth. They are the anatomical or physiological defects usually caused by errors in metabolism or development defects.
• Some congenital diseases are due to genetic defects and are often heritable.
• Examples include cleft lip, mental retardation, thalassemia, haemophilia, etc.
2. Acquired diseases
• The acquired diseases are developed after birth.
• They are the diseases caused by many factors like infection, metabolic factors, nutrient deficiency, radiation exposure, etc.
• The acquired diseases are of three types. They are communicable, non-communicable, and socially significant diseases.
Now, let you study some communicable, non-communicable, and socially significant diseases.
a) Communicable diseases
• The communicable diseases are the diseases due to an infectious agent or its toxic products capable of transmitting from man to man, animal to animal or from the environment to man or animal.
• Typhoid, tuberculosis, ascariasis, AIDS, hepatitis, rabies, etc are examples of communicable diseases.
Let you study some communicable diseases.
• Typhoid is an acute systemic infection caused by Salmonella typhi.
• Salmonella typhi is an infectious organism found only in human beings.
• Typhoid is characterised by fever for 3 to 4 weeks, relative bradycardia, headache, and splenomegaly.
• It is a very serious disease which kills about 10% of the infected population if antibiotics treatment is not included.
• It is a chronic systemic infection caused by several species of Mycobacteria, the most common of them being Mycobacterium tuberculosis.
• Mycobacterium is an infectious organism found in human beings as well as animals like cattle.
• Tuberculosis is very serious disease which kills many people throughout the world. It commonly occurs in the parts of the world where people live in an overcrowded situation.
• It is the emerging disease of developed countries due to AIDS.
• Tuberculosis is very common in developing countries like Nepal and India.
• Ascariasis is a common intestinal infestation caused by the adult Ascaris lumbricoides.
• It is characterised by abdominal pain, nausea, and other vague symptoms.
• It is the most common helminthic infestation.
• It is not common in developed countries like America, England, Germany, Spain, Saudia, Qatar, where water supplies and sanitation are good.
• AIDS is a fatal communicable disease caused by a virus known as HIV (Human Immunodeficiency Virus).
• HIV is an infectious organism found in human beings.
• HIV destroys the body’s immunity (defence against infections).
• The origin of HIV/AIDS is not clear. AIDS was first reported in USA.
• AIDS is widely distributed throughout the world. Worldwide, around 40 million people are living with HIV/AIDS and more than 20 million people have already died from AIDS.
• The hepatitis is a kind of communicable disease mainly characterised by the inflammation of liver.
• It may be acute when it lasts less than 6 months and chronic when it persists longer.
• There are two major types of hepatitis viral and toxic.
b) Non-communicable diseases
• Non-communicable diseases are diseases due to various risk factors and do not transfer from one person to another.
• There are various kinds of non-communicable diseases. They are
i) Deficiency disorders
• They are due to deficiency of various nutrients. For example, protein-energy malnutrition, anaemia, Beri-Beri, mineral deficiency diseases, etc.
ii) Metabolic diseases
• They are due to disorders of metabolism. For example, diabetes, hypertension, obesity, hormonal disorders, etc.
• Cancers are due to abnormal and uncontrolled growth and multiplication of body tissues. For example, lung cancer, breast cancer, colon cancer, etc.
iv) Degenerative diseases
• They are due to abnormal degeneration of body tissues. For example, atherosclerosis, degenerative brain diseases, joint diseases (osteoarthritis), etc.
v) Psychiatric diseases
• They are due to abnormalities in thinking, perception, mood, memory or behaviour.
c) Socially significant diseases
• The socially significant diseases are the conditions which lead to many disease states, distress, and suffering to an individual as well as the people around him and his society.
• For example, smoking, alcoholism, and drug abuse are some examples of socially significant diseases.
• They cause significant distress and suffering not only to an individual but also to his relatives, neighbours, and his society.
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