Human Health And Disease Class 12 Notes

What Is Health?

In simple terms, Health can be defined as free from all diseases and infections. According to the World Health Organization (WHO), health is not only the absence of disease or illness. It is a state of an active and energetic condition including the physical, mental, and social well being. A balanced diet and regular exercise play an important role in maintaining a good health of an individual. There are many factors which affect health, such as:

  • Poorly balanced diet.
  • Genetic Disorders.
  • Stress, and anxiety.
  • Infection from pathogens.
  • Intake of unhealthy and unhygienic food.
  • Lack of exercise and other physical activities.

To maintain a good health, an individual should include a healthy and balanced diet, maintain personal hygiene along with regular exercise and other physical activities. Everyone should be aware of the different types of diseases and their effects.

Read More: Important Questions for Class 12 Chapter 8: Human Health and Diseases

What are Diseases?

A disease is an abnormal condition affecting a healthy living organism. It is broadly divided into infectious and non-infectious.

Infectious diseases- These diseases are caused by the pathogens, such as bacteria, virus, fungi, parasites and can be easily transmitted from one person to another, hence it is also known as a contagious or communicable disease. Common Cold, Tuberculosis, flu, ringworm, malaria are some examples of infectious diseases.

Non-infectious diseases- Diseases which cannot be transmitted from one person to another are called non-infectious disease, it is also known as a noncommunicable disease. These diseases can be either caused by genetic disorders, unhealthy diets, lack of physical activity and few environmental factors.

Some Common Diseases In Humans

  • A pathogenic bacterium known as Salmonella typhi is known to cause typhoid in humans. This fever can be confirmed by Widal test
  • Pneumonia is caused by Streptococcus pneumoniae and Hemophilus influenza
  • Rhinovirus, a group of virus, is known to cause one of the most of infectious ailments in humans, cold.
  • Plasmodium, a small protozoan causes malaria. Another protozoan, Entamoeba histolytica causing amoebiasis (amoebic dysentery)
  • Ascaris(an intestinal parasite) causes ascariasis
  • Wuchererta, the filarial worm causes filariasis or elephantiasis


Immunity is defined as the ability of the body to protect, defend and fight against invading pathogens like bacteria, virus, and other foreign bodies and toxic substances. There are two types of immunity.

  • Innate immunity – non specific defence type of immunity present at the time of birth achieved by the provision of 4 barrier types – the physical barrier, physiological barrier, cellular barriers, cytokine barrier
  • Acquired immunity – pathogen specific immunity that is characterized by memory.

Active and Passive Immunity

Active immunity is where the host produces antibodies in the form of dead or living microbes when it is exposed to antigens. It is a slow process, taking time to provide its full effective response. Passive immunity, on the other hand, is the immunity where ready-made antibodies are given directly to protect the body against any foreign agents.


  • Acquired Immuno Deficiency Syndrome is caused by HIV(Human Immunodeficiency Virus) a member of the retrovirus group.
  • It is generally transmitted through sexual contact with infected person, blood transfusion with contaminated blood and its products, through the share of infected needles, from the infected mother to her child through the placenta. ELISA(Enzyme-linked immunosorbent assay)  is the diagnostic test for AIDS

Also  See: Cancer, Adolescence and Drug Abuse

For More Information On Vaccines and Antibiotic, Watch The Below Video:

Few Important Questions

  • Define Immunity and its types?
  • Define Addiction and Dependence?
  • What is Elisa? and what it is used for?
  • What is Cancer? Explain in brief about the types, diagnosis and treatment available for cancer?
  • List out the causes, symptoms, and available treatment for Influenza.

Learn more about human health and different types of disease from the topics given below:

Frequently asked Questions on CBSE Class 12 Biology Notes: Health Disease

What are ‘Genetic disorders’?

Genetic disorders occur when a mutation affects your genes or when you have the wrong amount of genetic material.

What is ‘Immunity’?

Immunity can be defined as a complex biological system endowed with the capacity to recognize and tolerate whatever belongs to the self.

What is ‘AIDS’?

Acquired Immuno Deficiency Syndrome is caused by HIV (Human Immunodeficiency Virus) a member of the retrovirus group.

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