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Human Health and Disease

NCERT Class 12 Biology Chapter 7

Human Health and Disease for Class 12 Biology and NEET: common diseases, immunity and vaccines, AIDS, cancer, and drug, alcohol and tobacco abuse.

7 topics Updated 8 Nov 2026

For: Class 12 and NEET, unless a topic says otherwise

In the syllabus: NEET Class 12 syllabus

With your textbook

NCERT Biology (Class 12), Chapter 7 “Human Health and Disease”, reprint 2026-27.

Open the official NCERT chapter (PDF, 4.5 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. Health and disease

    Health as complete physical, mental and social well-being, what affects it, and infectious and non-infectious diseases.

    NEET only 8 min read 3 solved examples 7 practice questions

  2. Common diseases in humans

    Common diseases in humans for Class 12 Biology and NEET: typhoid, pneumonia, common cold, malaria life cycle, amoebiasis, ascariasis, filariasis, ringworm.

    NCERT Section 7.1 16 min read 4 solved examples 8 practice questions

  3. Dengue and chikungunya

    The viruses, how mosquitoes spread them, symptoms, severe dengue, how the two differ, and mosquito control.

    NEET only 10 min read 3 solved examples 7 practice questions

  4. Immunity

    Immunity for Class 12 Biology and NEET: innate and acquired immunity, antibody structure diagram, active and passive, vaccines, allergies, lymphoid organs.

    NCERT Section 7.2 14 min read 3 solved examples 9 practice questions

  5. HIV and AIDS

    HIV and AIDS for Class 12 Biology and NEET: how HIV differs from AIDS, how the retrovirus spreads and multiplies, helper T-cell loss, ELISA and prevention.

    NCERT Section 7.3 11 min read 3 solved examples 8 practice questions

  6. Cancer

    Cancer for Class 12 Biology and NEET: contact inhibition, benign and malignant tumors, metastasis, carcinogens and oncogenes, detection and treatment.

    NCERT Section 7.4 10 min read 3 solved examples 8 practice questions

  7. Drug, alcohol and tobacco abuse

    Drugs and alcohol abuse for Class 12 Biology and NEET: opioids, cannabinoids, cocaine, tobacco, adolescence, addiction, effects and prevention.

    NCERT Section 7.5 16 min read 3 solved examples 8 practice questions

Key formulas in this chapter

Health and disease

  • health: complete physical, mental and social well-being
  • affects health: genetic disorders, infections, life style
  • infectious: easily transmitted from one person to another
  • non-infectious: cancer, the major cause of death

Common diseases in humans

  • typhoid: bacterium; food and water; Widal test
  • pneumonia: bacteria; alveoli fill with fluid
  • common cold: rhinoviruses; nose and respiratory passage, not the lungs (NCERT)
  • malaria: protozoan; female mosquito; haemozoin, fever
  • ringworm: fungi; dry, scaly, itchy lesions
  • filariasis: filarial worm; lymphatic vessels of legs

Dengue and chikungunya

  • dengue: four serotypes; usually mosquito-borne
  • dengue: about 1 in 4 infected fall sick
  • severe dengue: about 1 in 20 of those who fall sick
  • chikungunya: virus; fever and joint pain
  • prevention: remove breeding sites; protect against daytime bites

Immunity

  • basic antibody unit: HL (2 heavy, 2 light chains)
  • innate: non-specific; acquired: specific, memory
  • humoral: B-cells, antibodies; CMI: T-cells
  • active: own antibodies; passive: ready-made
  • allergy: IgE antibodies; histamine and serotonin from mast cells
  • primary lymphoid organs: bone marrow, thymus

HIV and AIDS

  • AIDS: Acquired Immuno Deficiency Syndrome
  • HIV: retrovirus; envelope around an RNA genome
  • viral RNA → viral DNA: reverse transcriptase
  • HIV enters macrophages and helper T-cells
  • time-lag to symptoms: usually 5–10 years
  • diagnosis: ELISA

Cancer

  • contact inhibition: lost in cancer cells
  • benign: stays in place; malignant: invades
  • metastasis: spread through the blood
  • carcinogens: physical, chemical, biological
  • c-onc (proto oncogenes): in normal cells
  • treatment: surgery, radiotherapy, chemotherapy
  • immunotherapy: α-interferon

Drug, alcohol and tobacco abuse

  • opioids: receptors in CNS and gut; heroin a depressant
  • cannabinoids: receptors mainly in the brain
  • cocaine: interferes with dopamine transport
  • nicotine: adrenaline, nor-adrenaline released
  • smoking: more CO, less haem-bound oxygen
  • adolescence: 12–18 years
  • dependence: withdrawal syndrome when stopped

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