Human Health and Disease Class 12 Notes is the most valuable asset of human life. According to the World Health Organization (WHO), health is a state of complete physical, mental, and social well-being, not merely the absence of disease. In our daily life, humans are continuously exposed to various disease-causing agents like bacteria, viruses, fungi, and parasites.
This chapter explains what health is, what diseases are, how diseases spread, how the immune system protects us, and how we can prevent diseases. This chapter is very important for CBSE board exams and NEET.

Table of Contents

Human Health and Disease Class 12 Notes | CBSE Biology

1. Health

Health means the proper functioning of the body and mind.

Factors Affecting Health

Genetic factors – inherited diseases
Lifestyle – diet, exercise, stress, sleep
Environment – pollution, sanitation
Social conditions – poverty, education, healthcare

Good health increases efficiency, longevity, and quality of life.

2. Disease

A disease is a condition in which normal functioning of the body is disturbed.

Types of Diseases

Diseases are broadly classified into two types:

(A) Congenital Diseases

Present since birth
Caused due to genetic defects
Example: Haemophilia, Colour blindness

(B) Acquired Diseases

Develop after birth
Further divided into:

(i) Infectious Diseases

Caused by pathogens
Spread from one person to another
Example: Tuberculosis, Malaria, COVID-19

(ii) Non-Infectious Diseases

Do not spread
Caused by lifestyle or deficiency
Example: Cancer, Diabetes, Heart disease

3. Infectious Agents

Different pathogens cause different diseases:

Pathogen	Example Disease
Bacteria	Typhoid, TB
Virus	AIDS, Dengue
Protozoa	Malaria
Helminths	Ascariasis
Fungi	Ringworm

4. Common Human Diseases

(A) Bacterial Diseases

Typhoid

Caused by Salmonella typhi
Spread through contaminated food and water
Symptoms: High fever, weakness, stomach pain
Diagnosis: Widal test

Pneumonia

Caused by Streptococcus pneumoniae
Affects lungs
Symptoms: Fever, cough, breathing difficulty

(B) Viral Diseases

Common Cold

Caused by Rhinovirus
Spread through air
Symptoms: Sneezing, cough, runny nose

AIDS

Caused by HIV (Human Immunodeficiency Virus)
Attacks immune system
Spread through blood, sexual contact, infected needles
No cure, but preventable

(C) Protozoan Disease

Malaria

Caused by Plasmodium
Spread by female Anopheles mosquito
Symptoms: Fever with chills, sweating

(D) Helminthic Disease

Ascariasis

Caused by Ascaris lumbricoides
Symptoms: Abdominal pain, anemia

(E) Fungal Disease

Ringworm

Caused by fungi (Microsporum, Trichophyton)
Symptoms: Itchy circular patches

5. Modes of Transmission of Diseases

Diseases spread through:

Air – cold, tuberculosis
Water & food – cholera, typhoid
Physical contact – ringworm
Sexual contact – AIDS
Vectors – mosquito (malaria, dengue)

6. Immunity

Immunity is the ability of the body to fight against pathogens.

Types of Immunity

(A) Innate Immunity

Present from birth
Non-specific
Includes skin, mucus, stomach acid, phagocytes

(B) Acquired Immunity

Develops after infection or vaccination
Specific response

Active Immunity

Body produces its own antibodies
Example: After vaccination

Passive Immunity

Antibodies received from outside
Example: Mother to child via placenta

7. Immune System Components

Lymphocytes (B-cells & T-cells)
Antibodies
Lymphoid organs (spleen, thymus, lymph nodes)

8. Vaccination

Vaccines contain weakened or killed pathogens.
They stimulate immune response without causing disease.

Examples:

Polio vaccine
BCG (Tuberculosis)
Hepatitis B vaccine

9. Allergies

Allergy is an exaggerated immune response.

Caused by allergens like pollen, dust
Symptoms: Sneezing, asthma, watery eyes
Chemical involved: Histamine

10. Autoimmune Diseases

Immune system attacks own body cells
Example: Rheumatoid arthritis

11. Immunodeficiency

When immune system is weak.

Example:

AIDS
Genetic disorders

12. Cancer

Cancer is uncontrolled cell division.

Causes:

Carcinogens (tobacco, radiation)
Genetic mutations

Types:

Benign
Malignant

Treatment:

Surgery
Chemotherapy
Radiotherapy

13. Drugs and Alcohol Abuse

Effects of Drugs:

Nervous system damage
Addiction
Social problems

Tobacco:

Causes lung cancer
Nicotine causes addiction

14. Prevention of Diseases

Balanced diet
Vaccination
Personal hygiene
Clean environment
Awareness

Important Exam-Oriented Points

HIV attacks helper T-cells
Malaria vector: Female Anopheles mosquito
Allergy mediator: Histamine
Vaccine provides active acquired immunity

Frequently Asked Questions (FAQs)

Q1. What is health?
Health is a state of physical, mental, and social well-being.

Q2. Name any two bacterial diseases.
Typhoid, Pneumonia.

Q3. What causes AIDS?
Human Immunodeficiency Virus (HIV).

Q4. What is vaccination?
Artificial introduction of antigen to develop immunity.

Conclusion

The chapter Human Health and Disease helps students understand how the human body maintains health and how diseases affect it. Knowledge of immunity, vaccination, and disease prevention is essential not only for exams but also for real life. A healthy lifestyle, awareness, and scientific understanding are the keys to a disease-free life.

🔴 Important Repeated Questions

Class 12 Biology – Human Health and Disease

⭐ Very Short Answer Questions (1 Mark)

Define health according to WHO.
Name the causative agent of typhoid.
Which mosquito transmits malaria?
Name the virus that causes AIDS.
Which cells are attacked by HIV?
What is an allergen?
Name the chemical released during allergic reactions.
What type of immunity is provided by vaccines?
Name one fungal disease in humans.
What is the full form of AIDS?

⭐ Short Answer Questions (2–3 Marks)

Differentiate between infectious and non-infectious diseases.
Write any two symptoms of typhoid.
Explain innate immunity with examples.
What is vaccination? Why is it important?
How does HIV affect the immune system?
Write two modes of transmission of diseases.
What is active immunity? Give one example.
Explain allergy and name the chemical involved.
Write two harmful effects of drug abuse.
What are pathogens? Name any two types.

⭐ Long Answer Questions (5 Marks)

(Most Repeated in CBSE Board Exams)

Explain common bacterial diseases in humans with symptoms and prevention.
Describe malaria with its causative agent, symptoms, and mode of transmission.
Explain the immune system and its components in detail.
What is AIDS? Explain its cause, symptoms, and prevention.
Describe acquired immunity and its types with examples.
Explain cancer – causes, types, and treatment.
Write a detailed note on drug and alcohol abuse and its effects.
Describe vaccination and how vaccines help in disease prevention.

⭐ Assertion–Reason Questions

(NEET + CBSE Objective Type)

Assertion (A): HIV causes AIDS.
Reason (R): HIV attacks helper T-cells.
Assertion (A): Vaccination does not cause disease.
Reason (R): Vaccines contain weakened pathogens.
Assertion (A): Malaria is a communicable disease.
Reason (R): It spreads through mosquito bite.
Assertion (A): Allergy is an immune response.
Reason (R): Histamine is released during allergy.

⭐ Case-Based Questions (CBSE Pattern)

A person suffering from high fever, weakness, and abdominal pain was diagnosed using Widal test.
(a) Name the disease
(b) Name the causative organism
(c) Mode of transmission
A child is given polio drops at birth.
(a) Name the immunity developed
(b) Type of immunity
(c) Importance of vaccination

⭐ NEET Important Points (Direct Questions)

HIV attacks CD4 T-lymphocytes
Allergy mediator → Histamine
Malaria vector → Female Anopheles mosquito
Vaccine provides → Active acquired immunity
Ringworm is caused by → Fungi

⭐ One-Line Revision Questions

Name the test used to diagnose typhoid.
Which organ is affected in pneumonia?
Name the causative agent of ringworm.
What type of disease is cancer?
Which immunity is present from birth?

🔥 Exam Tip for Students

👉 Questions from AIDS, Immunity, Vaccination, Malaria, Cancer are most frequently repeated.
👉 Diagrams + keywords improve marks.

Join my WhatsApp channel