Health and illness are two different things entirely. Illness results from an imbalance of the body's systems and may cause that imbalance to be more severe. That's why diseases are considered illnesses because they do not have a natural cure - it is a balance issue. Medical professionals define it as: 

Individuals experiencing this illness have a certain level of symptoms, which usually develop over time, such as fever or flu (more than 48 hours), abdominal pain, vomiting or diarrhoea (more than three days), and suppressed immune system function.

The most common diseases associated are cancer, heart disease, and diabetes when it comes to health. Without health, one will become ill sooner or later and eventually die.

The life of a healthy individual is more than just being strong, healthy, and able to function. The characteristics of a healthy individual are that of a person who can perform all physical, mental, and social tasks. This person will have no limiting factors that hinder them from performing daily tasks in all aspects of their lives.

Diseases are conditions resulting in pathological changes in living organisms. Certain diseases may be caused by viruses, bacteria, parasites, or fungi. Diseases can range from mild and self-limiting to severe and life-threatening conditions requiring medical treatment. Infections usually cause illnesses by certain organisms (pathogens) though pathogens cause not all illnesses. A disease is a situation in which the body cannot prevent the spread of infection and does not heal itself.

Diseases are further classified into two categories which are:

1. Infectious diseases: These diseases are caused by infections from several microorganisms.
   Some of the common infectious diseases are influenza, Malaria, typhoid, and tuberculosis.
2. Non-infectious diseases: These types of diseases may be caused by toxic/chemical agents, physical trauma, hereditary factors, or ageing. 
   Some common non-infectious communicable diseases are AIDS, cancer, coronary heart disease, and diabetes.

Communicable diseases are infections by pathogenic microorganisms transmitted from person to person. Some of the common communicable diseases are:

1. Some types of communicable diseases are HIV/AIDS, Cancer, Tuberculosis, Malaria and Leprosy.
2. Some illnesses inflict permanent disability or death. 

For example, AIDS can cause AIDS-related complex (ARC) or acquired immune deficiency syndrome (AIDS).

These are diseases caused by toxic/chemical agents, physical trauma, hereditary factors, or ageing and these diseases are not transmittable from person to person. Some of the common non-communicable diseases:

1. Some non-communicable diseases are Alzheimer's disease, Asthma, Cerebral palsy, Diabetes mellitus type 2 and Hypertension.
2. These diseases typically do not cure; they can only be treated. This is why Non-communicable diseases are also referred to as chronic conditions.

1. Diseases of the Nervous System: A human brain is the most complex organ that controls all cells in the body. Certain diseases are caused by disorders in the central nervous system like Alzheimer's Disease and Parkinson's Disease.
2. Diseases of the Circulatory System: Any disorder in the circulatory system is called heart disease, which includes problems related to blood vessels like coronary artery disease and peripheral vascular disease.
3. Diseases of the Respiratory System: This includes breathing disorders like asthma and bronchitis, pneumonia, etc., due to infection, allergy, or other factors, including pollution and chemical substances in the air.
4. Diseases of the Digestive System: Diseases of the digestive system are caused due to disorders such as ulcers, diarrhoea, diverticulitis, etc.
5. Diseases of the Genitourinary System: This type of Disease includes urine-like kidney stones, bladder and urinary tract infections, prostate infections, and erectile dysfunction.
6. Diseases of the Musculoskeletal System: The musculoskeletal system includes bones, joints, and muscles in the body that work together for movement and support various parts of the body. Some common diseases of this system are back pain, osteoarthritis, rheumatoid arthritis, etc.

Immunity is a condition or quality that protects an individual against certain diseases. Immunity means being protected from illness and diseases, so when an individual's immunity is weakened, they are at a higher risk of getting ill.

Active and Passive Immunity:

Active immunity is acquired when an individual is exposed to a particular disease and later develops antibodies, which provides resistance against the Disease.

Passive Immunity: This is induced by taking antibodies of an individual who has been exposed to a particular disease.

Viral infections are caused by viruses that attack human tissues and organs. These viruses directly infect the cells, multiplying using the host cell's DNA. As a result, the infected body parts go through multiple symptoms of fever, headaches, rash, malaise, to name a few, before they finally lead to the death of the infected body part or whole body.

The immune system produces antibodies to identify and neutralise infections from harmful organisms, thus preventing them from spreading throughout the body.

Antibiotics are drugs that fight bacteria and other inflammatory agents. They work similarly to vaccines, but antibiotics can only be used for those infections related to bacteria.

AIDS:

AIDS stands for acquired immunodeficiency syndrome. Acquired Immune Deficiency Syndrome disease is a disease that is caused due to a virus that attacks the immune system. The virus destroys the body's ability to defend itself against other illnesses and infections. Furthermore, AIDS can be transmitted through unprotected sex, sharing needles, blood transfusions, or an infected mother to her child.

Cancer:

Cancer is usually a disease that presents signs of uncontrolled, abnormal cell division in the body. These can result in abnormal malignant or cancerous cells due to uncontrollable cell division. The cells affected by cancer have a high risk of spreading to other body regions and causing damage and death to the individual.

Vaccines are medical preparations made from weak microorganisms or recombinant viruses used to prevent infection so that an individual does not develop immunity towards it. Instead, individuals develop immunity when they receive immunisation to a particular agent.

We should practice precautions and ways to live a healthy life. Maintaining a healthy diet, eating less fat and sugar, decreasing alcohol intake, and regular exercising is necessary. Regular medical checkups are essential in the prevention of diseases. You can prevent complications by taking your medications as advised by your doctor and leading a healthy lifestyle with less smoking and drug use. If you adopt a healthy lifestyle, you will stay away from diseases and have a longer life span.

All these diseases can easily be prevented and treated if proper care is taken at the right time and suitable treatment options. Human Health and Disease NCERT talks about essential topics like Human Health and Disease, Causes of diseases, and discusses their prevention. This article gives a good insight into all the possible aspects that come into play when we talk about human health and disease and its causes and treatment. In short, browsing through this page will help you gain information on the different aspects of human health and disease to be aware of these topics' basic knowledge. Download the MSVGo app today to make your learning easy and get your doubts clarified in no time.