Diseases and its Types | General Test Preparation for CUET - CUET Commerce PDF Download

What is Disease?

"A disease is a state wherein the regular function of cells, tissues, and organs is impaired. Typically, diseases are identified by their observable signs and symptoms, representing a departure from normal health. Broadly speaking, a disease can be described as any harmful deviation from the usual functioning of an organism. Symptoms of a disease can range from mild to severe, depending on the specific condition, making it essential to understand what constitutes normal function in order to recognize disease. Diseases typically have multiple causative factors rather than a singular origin. Symptoms, such as headaches, coughing, cold symptoms, or weakness, often manifest shortly after the onset of a disease, although the timing can vary depending on its severity."

Classification of Diseases

Types of Diseases

Diseases can be of two types

1. Infectious Diseases: Diseases that spread from one person to another are called communicable diseases. They are usually caused by microorganisms called pathogens (fungi, rickettsia, bacteria, viruses, protozoans, and worms). When an infected person discharges bodily fluids, pathogens may exit the host and infect a new person (sneezing, coughing etc). Examples include Cholera, chickenpox, malaria etc.

2. Non-infectious Diseases: These diseases are caused by pathogens, but other factors such as age, nutritional deficiency, gender of an individual, and lifestyle also influence the disease. Examples include hypertension, diabetes, and cancer. They do not spread to others and they restrain within a person who has contracted them. Alzheimer’s disease, asthma, cataract and heart diseases are other non-infectious diseases.

Based on these above classifications, a disease may fall into any number of these classifications.

Degenerative Diseases

• They are mainly caused by the malfunctioning of vital organs in the body due to the deterioration of cells over time. Diseases such as osteoporosis show characteristics of degenerative diseases in the form of increased bone weakness. This increases the risk of bone fractures.
• When degeneration happens to the cells of the central nervous system, such as neurons, the condition is termed as a neurodegenerative disorder. Alzheimer’s is a prominent example of this disorder. Degenerative diseases are usually caused by ageing and bodywear. Others are caused by lifestyle choices and some are hereditary.

Allergies

• An allergic reaction arises when the body becomes hypersensitive to certain foreign substances called allergens. This usually happens when the immune system reacts abnormally to any seemingly harmless substances. Common allergens include dust, pollen, animal dander, mites, feathers, latex and also certain food products like nuts and gluten. 
• Peanuts and other nuts have the capability to cause severe allergic reactions that may induce life-threatening conditions such as difficulty in breathing, tissues swelling up and blocking the airways and anaphylaxis shock.
• Other common and less life-threatening symptoms include coughing, sneezing, running nose, itchy and red eyes, and skin rashes. One of the best examples of this allergic reaction is asthma. Sometimes, bee stings and ant bites also trigger allergies. Consumption of shellfish and certain medications can induce allergic reactions.
• Asthma is a chronic disease, that mainly affects the bronchi and bronchioles of the lungs. One of the factors responsible for this is airborne allergens such as pollens or dust. Symptoms include difficulty in breathing, wheezing, and coughing.

Deficiency Diseases

• They occur due to the deficiencies of hormones, minerals, nutrients, and vitamins. 
• For example, diabetes occurs due to an inability to produce or utilize insulin, goitre is mainly caused by iodine deficiency, and kwashiorkor is caused by a lack of proteins in the diet. Vitamin B1 deficiency causes beriberi.

Goitres

It is an abnormal enlargement of the thyroid gland by blocking the oesophagus or other organs of the chest and neck. This causes difficulty in breathing and eating.

Blood Diseases

• Blood contains plasma, white blood cells, platelets and red blood cells. When any of these components are affected, it can lead to blood disorders. For instance, red blood cells are destroyed when a person contracts sickle cell disease. 
• The red blood cells are distorted into the shape of a sickle (hence, the name) and they lose their ability to carry oxygen. Consequently, this disease is characterized by symptoms similar to chronic anaemia, such as shortness of breath and tiredness.
• Other diseases such as eosinophilic disorders, leukaemia, myeloma (cancer of plasma cells in bone marrow), Sickle Cell Anemia, Aplastic Anemia, Hemochromatosis and Von Miller and Disease (blood-clotting disorder) fall under this classification.
• General Symptoms: Pale skin, swelling of lymph nodes, fever, bleeding, bruising, skin rashes, etc.

Disease-Causing Agents

We have seen the classification of different entities based on various characteristics, for simplification, we classify organisms to group them together and study about them as a class. Similarly, diseases are caused by different microorganisms and can be classified as diseases caused by bacteria, fungi, viruses etc. Some diseases are also caused by multicellular organisms such as worms.
Listed below are a few diseases and the disease-causing agents