9th Class Science Why do we fall Ill? Types of Diseases

Types of Diseases

Category : 9th Class

*         Types of Diseases


There are basically four types of diseases such as chronic diseases, acute diseases, acquired diseases, and congenital diseases.

In this part we will discuss about all the four types of diseases.

  • Chronic Diseases: The diseases, which last for long time and are almost incurrable are called chronic disease. For example, TB, AIDs, cancer, leprosy, etc are the example of chronic diseases. The chronic diseases affect the health drastically. The person become weak and lose weight. It also reduces our ability to learn and understand the matters and reduce the memory power.
  • Acute Diseases: The diseases which get cured in short time is called acute diseases. The diseases like common cold, influenza, viral, are acute diseases. The acute diseases do not cause any major effect on the health of the affected person.
  • Acquired Diseases: The diseases which developed after birth is called acquired diseases. It is further classified in two types Communicable and

Non Communicable diseases. The diseases which spread from one person to another is called communicable diseases. These diseases are caused by microorganism such as fungi, bacteria, protozoans and viruses. It may spread through air, water, food and insects. The non communicable diseases are those which do not spread from one person to another. The non communicable diseases is offourtypes as organic diseases, deficiency diseases, allergies and cancer.


*           Infectious Diseases

The microorganisms which carry the pathogens that causes diseases is called infectious agent. Some of the infectious agents are virus, bacteria, fungi, protozoans, etc. Some of the common diseases caused by virus are common cold, influenza, dengue, AIDS, etc. The diseases caused by bacteria are cholera, TB, anthrax, tyhpoid, etc. These pathogens cause the diseases either by damaging the tissue or by toxin secretion. The virus is considered as the border line between living and non living organism. When they are inside the human cell they acts like a living and when they are outside they behave like non living. The diseases caused by bacteria can be cured by taking antibiotic, where as the diseases caused by virus can be cured by taking antiviral called interferon. The anti bodies act inside the cell, where as interferons act outside the cells. It acts very quickly against the viruses, but the action is temporary.


The various diseases caused by different microorganisms are given below in the table:


Sr. No. Microorganisms Various Diseases
1 Bacteria Chloera, Typhoid, TB, Anthrax, Tetnus, Food poisoning, Meningitis, diphtheria, etc
2 Virus AIDS, Common Cold, Influenza, Hepatitis-B, Chicken Pox, Measles, Mumps, etc
3 Fungi Skin diseases, Ring worm, etc
4 Protozoan?s Malaria, Dysentry, Sleeping sickness, Kala - azar
5 Worms Elephantiasis, Intestinal infections


*           Means of Spread of Diseases

There are various means by which infectious disease spread from one person to another. They can spread through air, water, contaminated food, etc. Some of the disease like common cold, pneumonia and TB spreads through air. If an infected person sneezes or cough in open air, the person standing nearby get infected. The other diseases like cholera, dysentery spread through contaminated water. The bacteria enters from the body of infected person to the healthy person and cause the disease. The disease like AIDS, Syphilis etc are sexually transmitted disease. They get transmitted when the infected person has sexual intercourse with the healthy person. The other casual physical contacts like hand shakes, hugging, wrestling can also cause such disease. Many disease like malaria, are caused by the biting of mosquito.



*           Organ Specific and Tissue Specific Diseases

There are various means by which disease causing microorganism enters into our body. Different microbes goes to different parts of our body. If they enter from air via nose, they are likely to go to lungs, which is seen in case of bacteria that cause TB. If they enter through mouth , they lie in the inner lining of guts and can cause typhoid or if they go to liver they can cause jaundice. Malaria causing microbes enters into our body by biting of mosquitoes.

On the other hand, tissue specific disease depends on the fact that the immune system of the body become active and recruits many cell to the affected tissue to destroy the disease causing microbes, which is called inflammation. As a part of this process, there are local effects such as swelling, pains and most general effects is fever. In case of HIV infection the viruses goes to the immune system and damage its function. The severity of the disease depends on the number of microbes in the body. If the number of microbes is less, then the disease is minor and if the number of microbes is in large number, then the disease can be major and can be life taking. It is the immune system of the body that determines the number of microbes in the body. The body with strong immune system will have lesser number of microbes and hence is less prone to the disease.


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