Human Health and Disease NEET Notes 2027 PDF and Key Points

Human Health and Disease is Chapter 7 of NCERT Class 12 Biology and part of Unit 8, Biology and Human Welfare, of the NEET UG syllabus. These notes cover common human diseases and their pathogens, the malaria life cycle, innate and acquired immunity, vaccination, allergy, lymphoid organs, AIDS, cancer and drug, alcohol and tobacco abuse, with a free notes PDF.

Human Health and Disease NEET Notes

Section-wise key points from NCERT Chapter 7, comparison tables, high-yield facts and common mistakes for NEET 2027 revision.

Human Health and Disease at a Glance

Item	Details
NEET UG syllabus unit	Unit 8: Biology and Human Welfare
NCERT textbook	Biology, Class 12, Chapter 7 (rationalised book)
Other chapters in the unit	Microbes in Human Welfare (Chapter 8)
Syllabus topics	Health and disease; pathogens; parasites causing human diseases (malaria, filariasis, ascariasis, typhoid, pneumonia, common cold, amoebiasis, ringworm, dengue, chikungunya); basic concepts of immunology: vaccines; cancer, HIV and AIDS; adolescence, drug and alcohol abuse; tobacco abuse
Official chapter	NCERT Chapter 7
Notes PDF	View PDF

The topic list follows the NEET UG 2026 syllabus released by the National Medical Commission (NMC) on 22 December 2025, which stays the reference until the 2027 syllabus is out. The full list is on the NEET syllabus page.

What is health?

Health is a state of complete physical, mental and social well-being, not simply the absence of disease or physical fitness.

Early Greeks such as Hippocrates and the Indian Ayurveda system held that health was a balance of ‘humors’. William Harvey’s discovery of blood circulation and thermometer readings disproved the ‘good humor’ idea.
The mind influences the immune system through the neural and endocrine systems, so mental state can affect health.
Health is affected by genetic disorders, infections and lifestyle (food, water, rest, exercise and habits).
Balanced diet, personal hygiene, regular exercise, yoga, vaccination, waste disposal, vector control and hygienic food and water help maintain health.
Diseases are infectious (easily transmitted from person to person, e.g. AIDS, which is fatal) or non-infectious; among non-infectious diseases cancer is the major cause of death.

Common Diseases in Humans and Their Pathogens

Pathogens are disease-causing organisms such as bacteria, viruses, fungi, protozoans and helminths; most parasites are pathogens because they harm the host they live in or on.

Disease	Pathogen	Spread	Key symptoms and facts
Typhoid	Salmonella typhi (bacterium)	Contaminated food and water; enters the small intestine, then other organs through blood	Sustained high fever (39 to 40 °C), weakness, stomach pain, constipation, headache, loss of appetite; intestinal perforation in severe cases; confirmed by Widal test
Pneumonia	Streptococcus pneumoniae and Haemophilus influenzae (bacteria)	Inhaling droplets/aerosols of an infected person; sharing glasses and utensils	Infects alveoli, which fill with fluid; fever, chills, cough, headache; lips and nails may turn grey to bluish
Common cold	Rhino viruses	Inhaled droplets from cough or sneeze; contaminated objects such as pens, cups, doorknobs, keyboards	Infects nose and respiratory passage, not the lungs; nasal congestion, sore throat, hoarseness, cough; lasts 3 to 7 days
Malaria	Plasmodium vivax, P. malaria, P. falciparum (protozoans)	Bite of infected female Anopheles mosquito	Chill and high fever recurring every 3 to 4 days; malignant malaria by P. falciparum is the most serious and can be fatal
Amoebiasis (amoebic dysentery)	Entamoeba histolytica (protozoan) in the large intestine	Food and water contaminated by faeces; houseflies are mechanical carriers	Constipation, abdominal pain and cramps, stools with excess mucous and blood clots
Ascariasis	Ascaris, the common round worm (helminth)	Eggs passed in faeces contaminate soil, water and plants; infection through contaminated water, vegetables and fruits	Internal bleeding, muscular pain, fever, anaemia, blockage of the intestinal passage
Filariasis (elephantiasis)	Wuchereria bancrofti and W. malayi, filarial worms (helminths)	Bite of female mosquito vectors	Slowly developing chronic inflammation, usually of lymphatic vessels of the lower limbs; genital organs also often affected
Ringworm	Fungi of the genera Microsporum, Trichophyton and Epidermophyton	Soil, or towels, clothes or comb of infected people	Dry, scaly lesions on skin, nails and scalp with intense itching; heat and moisture help growth, e.g. in the groin or between toes

Other bacterial diseases named by NCERT: dysentery, plague and diphtheria.
Dengue and chikungunya are vector-borne diseases spread by Aedes mosquitoes.

Life Cycle of Plasmodium

Plasmodium enters the human body as sporozoites (infectious form) through the bite of an infected female Anopheles mosquito.
The parasites first multiply in liver cells and then attack red blood cells, causing them to rupture.
Rupture of RBCs releases a toxic substance, haemozoin, which causes the chill and high fever recurring every three to four days.
When a female Anopheles bites an infected person, the parasites enter the mosquito, develop and multiply to form sporozoites stored in its salivary glands.
The parasite needs two hosts, human and mosquito; the female Anopheles is also the vector.

How are infectious diseases prevented and controlled?

Personal and public hygiene, avoiding contact with infected people, controlling vectors, vaccination and drugs are the main tools against infectious diseases.

Personal hygiene: keeping the body clean and consuming clean water, food, vegetables and fruits.
Public hygiene: proper disposal of waste and excreta, periodic cleaning and disinfection of water reservoirs, pools, cesspools and tanks, and hygiene in public catering. These matter most for food- and water-borne diseases such as typhoid, amoebiasis and ascariasis.
Air-borne diseases such as pneumonia and the common cold: also avoid close contact with infected persons or their belongings.
Vector control for malaria and filariasis: avoid stagnant water, clean household coolers, use mosquito nets, introduce fish like Gambusia that eat mosquito larvae, spray insecticides in ditches and swamps, and fit wire mesh on doors and windows.
Vaccines and immunisation completely eradicated smallpox and have largely controlled polio, diphtheria, pneumonia and tetanus. Antibiotics and other drugs treat many infections.

Immunity: Innate and Acquired

Immunity is the overall ability of the host, conferred by the immune system, to fight disease-causing organisms; it is of two types, innate and acquired.

Barrier of innate immunity	Examples
Physical	Skin; mucus coating of the epithelium of respiratory, gastrointestinal and urogenital tracts
Physiological	Acid in the stomach, saliva in the mouth, tears from the eyes
Cellular	Polymorpho-nuclear leukocytes (PMNL, neutrophils), monocytes and natural killer cells in blood; macrophages in tissues; they phagocytose and destroy microbes
Cytokine	Interferons secreted by virus-infected cells, which protect non-infected cells from further viral infection

Feature	Innate immunity	Acquired immunity
Specificity	Non-specific	Pathogen-specific
When present	At birth	Develops after exposure
Memory	No	Yes: primary response is low intensity; secondary (anamnestic) response is highly intensified

Humoral and Cell-mediated Immunity

B-lymphocytes produce antibodies in response to pathogens. T-cells do not secrete antibodies but help B-cells produce them.
Each antibody has four peptide chains, two light and two heavy, so it is written H2L2. Types include IgA, IgM, IgE and IgG.
Antibody-mediated immunity is called the humoral immune response because antibodies are in the blood.
Cell-mediated immunity (CMI) is mediated by T-lymphocytes and is responsible for graft rejection, because the body distinguishes ‘self’ from ‘non-self’.
Before a transplant, tissue matching and blood group matching are essential, and the patient takes immuno-suppressants for life.

Active and Passive Immunity, Vaccination

Active immunity develops when the host’s own body makes antibodies after exposure to antigens; passive immunity is given by ready-made antibodies.

Feature	Active immunity	Passive immunity
Antibodies	Produced by the host’s own body	Ready-made antibodies given directly
Speed	Slow; takes time to give full response	Immediate protection
Examples	Natural infection; deliberate injection of microbes in immunisation	Colostrum (rich in IgA) for the newborn; antibodies passing to the foetus through the placenta; antitoxin for tetanus; anti-venom for snakebite

Vaccination is based on the memory of the immune system. A vaccine contains antigenic proteins of a pathogen or inactivated/weakened pathogens.
Vaccines produce antibodies and also memory B- and T-cells that recognise the pathogen quickly on later exposure.
When a quick response is needed, as in tetanus, preformed antibodies or antitoxin are injected; this is passive immunisation.
Recombinant DNA technology produces antigenic polypeptides in bacteria or yeast, allowing large-scale vaccine production, e.g. hepatitis B vaccine from yeast.

Allergies and Autoimmunity

Allergy is the exaggerated response of the immune system to certain antigens in the environment, called allergens; autoimmunity is when the body attacks its own cells.

Common allergens: mites in dust, pollens and animal dander.
Antibodies produced in allergy are of the IgE type.
Allergy is due to the release of chemicals like histamine and serotonin from mast cells; symptoms include sneezing, watery eyes, running nose and difficulty in breathing.
Causes are found by exposing the patient to very small doses of possible allergens; anti-histamine, adrenalin and steroids quickly reduce symptoms.
More children in Indian metro cities suffer from allergies and asthma, possibly because of the protected environment early in life.
Autoimmune disease: due to genetic and other unknown reasons the body attacks self-cells; rheumatoid arthritis is an example.

Immune System in the Body: Lymphoid Organs

The human immune system consists of lymphoid organs, tissues, cells and soluble molecules like antibodies; it recognises foreign antigens, responds to them and remembers them.

Lymphoid organ	Type	Key points
Bone marrow	Primary	Main lymphoid organ where all blood cells, including lymphocytes, are produced
Thymus	Primary	Lobed organ near the heart, beneath the breastbone; large at birth and very small by puberty
Spleen	Secondary	Large bean-shaped organ with lymphocytes and phagocytes; filters blood by trapping blood-borne microorganisms; large reservoir of erythrocytes
Lymph nodes	Secondary	Small solid structures along the lymphatic system; trap microorganisms and antigens in lymph and tissue fluid and activate lymphocytes
Tonsils, Peyer’s patches of small intestine, appendix	Secondary	Sites where lymphocytes interact with antigens and proliferate into effector cells

Primary lymphoid organs are where immature lymphocytes differentiate into antigen-sensitive lymphocytes; bone marrow and thymus provide micro-environments for T-lymphocyte development and maturation.
Mucosa-associated lymphoid tissue (MALT) lines the respiratory, digestive and urogenital tracts and makes up about 50 per cent of the lymphoid tissue in the human body.

AIDS: Cause, Spread, Mechanism and Prevention

AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human Immuno deficiency Virus (HIV), a retrovirus with an envelope enclosing an RNA genome; it is acquired during life, not congenital.

AIDS was first reported in 1981.
Transmission: sexual contact with an infected person, transfusion of contaminated blood and blood products, sharing infected needles (intravenous drug abusers), and from infected mother to child through the placenta.
HIV/AIDS does not spread by mere touch or physical contact; it spreads only through body fluids.
The time lag between infection and AIDS symptoms may be a few months to many years, usually 5 to 10 years.

How HIV Damages the Immune System

HIV enters macrophages, where its RNA genome is copied into viral DNA by the enzyme reverse transcriptase.
The viral DNA is incorporated into the host cell’s DNA and directs the cell to make virus particles, so macrophages act as an HIV factory.
HIV also enters helper T-lymphocytes (TH), replicates, and progeny viruses attack more helper T-cells, so their number falls progressively.
The person suffers bouts of fever, diarrhoea and weight loss, then infections by bacteria (especially Mycobacterium), viruses, fungi and parasites like Toxoplasma.
Diagnosis: ELISA (enzyme linked immuno-sorbent assay) is widely used. Anti-retroviral drugs are only partially effective and can only prolong life.

Prevention

As AIDS has no cure, prevention is the best option.
In India the National AIDS Control Organisation (NACO) and NGOs educate people; WHO runs prevention programmes.
Steps: safe blood from blood banks, only disposable needles and syringes, free distribution of condoms, controlling drug abuse, advocating safe sex and regular HIV check-ups in susceptible populations.
Infected people need help and sympathy, not isolation.

Cancer: Tumours, Causes, Detection and Treatment

Cancer is the breakdown of the mechanisms that control cell growth and differentiation; cancer cells lose contact inhibition and keep dividing to form tumours.

Feature	Benign tumour	Malignant tumour
Spread	Stays confined to its original location	Invades and damages surrounding normal tissue
Damage	Causes little damage	Grows rapidly and starves normal cells by competing for nutrients
Metastasis	Absent	Present: sloughed cells travel through blood and start new tumours at distant sites

Carcinogens are physical, chemical or biological agents that transform normal cells into neoplastic cells.
Physical: ionising radiation (X-rays, gamma rays) and non-ionising radiation (UV) damage DNA.
Chemical: carcinogens in tobacco smoke are a major cause of lung cancer.
Biological: oncogenic viruses carry viral oncogenes. Cellular oncogenes (c-onc) or proto-oncogenes in normal cells can cause oncogenic transformation when activated.

Detection and Treatment

Biopsy and histopathological study of tissue; blood and bone marrow tests for increased cell counts in leukaemias.
Radiography (X-rays), CT (computed tomography, which uses X-rays to give a three-dimensional image) and MRI (strong magnetic fields and non-ionising radiation) detect cancers of internal organs.
Antibodies against cancer-specific antigens and molecular biology techniques that find genes for inherited susceptibility also help detection.
Treatment: surgery, radiation therapy, chemotherapy and immunotherapy; most cancers are treated by a combination of surgery, radiotherapy and chemotherapy.
Chemotherapeutic drugs have side effects such as hair loss and anaemia.
Tumour cells avoid the immune system, so patients are given biological response modifiers such as alpha-interferon, which activate the immune system.

Drugs, Alcohol and Tobacco Abuse

The commonly abused drugs are opioids, cannabinoids and coca alkaloids, mostly obtained from flowering plants and some from fungi.

Drug	Source	Action	How taken
Opioids, e.g. heroin (smack, diacetylmorphine)	Acetylation of morphine from the latex of poppy, Papaver somniferum	Bind opioid receptors in the CNS and gastrointestinal tract; heroin is a depressant that slows body functions	Snorting and injection
Cannabinoids (marijuana, hashish, charas, ganja)	Inflorescences of Cannabis sativa; flower tops, leaves and resin used in combinations	Interact with cannabinoid receptors, mainly in the brain; affect the cardiovascular system	Inhalation and oral ingestion
Cocaine (coke, crack)	Coca plant, Erythroxylum coca, native to South America	Interferes with transport of dopamine; potent CNS stimulant causing euphoria; excess causes hallucinations	Usually snorted

Other plants with hallucinogenic properties: Atropa belladonna and Datura.
Barbiturates, amphetamines and benzodiazepines, used as medicines for depression and insomnia, are often abused. Morphine is a very effective sedative and painkiller after surgery.
Tobacco contains nicotine, an alkaloid that stimulates the adrenal gland to release adrenaline and nor-adrenaline, raising blood pressure and heart rate.
Smoking is linked to cancers of the lung, urinary bladder and throat, bronchitis, emphysema, coronary heart disease and gastric ulcer; tobacco chewing to oral cancer.
Smoking raises carbon monoxide in blood and lowers haem-bound oxygen, causing oxygen deficiency.

Adolescence, Addiction and Dependence

Adolescence (roughly 12 to 18 years) is a vulnerable phase. Causes of drug and alcohol use include curiosity, adventure and experimentation, academic stress, the idea that it is ‘cool’, media, unstable families and peer pressure.
Addiction is a psychological attachment to effects like euphoria. Repeated use raises receptor tolerance, so higher doses are needed; even a single use can lead to addiction.
Dependence is the body’s tendency to show an unpleasant withdrawal syndrome (anxiety, shakiness, nausea, sweating) when regular use stops abruptly.

Effects and Prevention

Immediate effects: reckless behaviour, vandalism, violence; overdoses can cause coma and death from respiratory failure, heart failure or cerebral haemorrhage.
Intravenous users are much more likely to get AIDS and hepatitis B. Chronic drug and alcohol use damages the nervous system and liver (cirrhosis); use in pregnancy harms the foetus.
Anabolic steroid misuse in sport: in females, masculinisation, aggressiveness, mood swings, abnormal menstrual cycles, facial hair, deepening of voice; in males, acne, reduced testis size, decreased sperm production, breast enlargement, premature baldness, prostate enlargement; in adolescents, premature closure of long-bone growth centres.
Prevention: avoid undue peer pressure, education and counselling, seeking help from parents and peers, looking for danger signs, and seeking professional and medical help.

Most-asked Facts for NEET: Human Health and Disease

Revise these one-line facts from the NCERT chapter just before the exam.

Typhoid: Salmonella typhi; confirmed by the Widal test; Mary Mallon was ‘Typhoid Mary’.
Pneumonia: Streptococcus pneumoniae and Haemophilus influenzae; infects alveoli.
Common cold: rhino viruses; infects nose and respiratory passage, not lungs.
Malaria: Plasmodium enters as sporozoites via female Anopheles; haemozoin causes chill and fever.
P. falciparum causes malignant malaria.
Amoebiasis: Entamoeba histolytica; houseflies are mechanical carriers.
Filariasis (elephantiasis): Wuchereria bancrofti and W. malayi.
Ringworm: Microsporum, Trichophyton, Epidermophyton.
Gambusia fish eat mosquito larvae; dengue and chikungunya are spread by Aedes.
Interferons are the cytokine barrier against viruses.
Antibody structure: H2L2; types IgA, IgM, IgE, IgG.
Colostrum is rich in IgA; allergy involves IgE, histamine and serotonin from mast cells.
Hepatitis B vaccine is produced from yeast using recombinant DNA technology.
Primary lymphoid organs: bone marrow and thymus. MALT is about 50 per cent of lymphoid tissue.
HIV: retrovirus with RNA genome; reverse transcriptase; attacks helper T-cells; ELISA for diagnosis.
Cancer cells lose contact inhibition; metastasis is the spread of malignant tumours.
Alpha-interferon is a biological response modifier used in cancer therapy.
Heroin: diacetylmorphine from morphine of Papaver somniferum. Cocaine: Erythroxylum coca, affects dopamine transport.
Nicotine releases adrenaline and nor-adrenaline, raising blood pressure and heart rate.

Common Mistakes to Avoid

Watch for these mix-ups when you answer questions on this chapter.

Saying the common cold infects the lungs. Rhino viruses infect the nose and respiratory passage, not the lungs.
Naming the male Anopheles as the malaria vector. Only the female Anopheles transmits Plasmodium.
Saying Plasmodium enters humans as merozoites or gametes. It enters as sporozoites, the infectious form.
Mixing up the test names: Widal test is for typhoid; ELISA is for AIDS.
Calling vaccination passive immunity. Vaccination gives active immunity; antitoxin, snake anti-venom, colostrum and placental antibodies give passive immunity.
Linking allergy to IgA. Allergy involves IgE; colostrum is rich in IgA.
Listing the thymus or bone marrow as secondary lymphoid organs. They are primary; spleen, lymph nodes, tonsils, Peyer’s patches and appendix are secondary.
Saying HIV has a DNA genome. HIV is a retrovirus with an RNA genome, copied into DNA by reverse transcriptase.
Saying benign tumours metastasise. Only malignant tumours show metastasis.
Calling heroin a stimulant. Heroin is a depressant; cocaine is a stimulant of the CNS.
Mixing up Ascaris and Wuchereria spread. Ascaris spreads through contaminated food and water; Wuchereria through mosquito bites.

Download the AglaSem notes for Human Health and Disease (key notes and important questions with answers) free: View PDF

All chapters: NEET Biology notes
Full topic list: NEET syllabus
Practice: NEET question papers
Source text: NCERT Chapter 7 (NCERT, Class 12 Biology)

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Human Health and Disease NEET Notes FAQs

Which NCERT chapter is Human Health and Disease?

It is Chapter 7 of the NCERT Class 12 Biology textbook (rationalised book), in the Biology in Human Welfare unit together with Microbes in Human Welfare (Chapter 8).

Is Human Health and Disease in the NEET 2027 syllabus?

It is in the latest NEET UG syllabus (2026, released by NMC on 22 December 2025) under Unit 8, Biology and Human Welfare, covering pathogens and parasites, basic immunology and vaccines, cancer, HIV and AIDS, and drug, alcohol and tobacco abuse. Check the syllabus page once NMC releases the 2027 syllabus.

What is the difference between active and passive immunity?

In active immunity the body makes its own antibodies after exposure to antigens, through infection or vaccination; it is slow but lasting. In passive immunity ready-made antibodies are given, as in colostrum, placental transfer, tetanus antitoxin or snake anti-venom, so protection is immediate.

How does HIV cause immune deficiency?

HIV enters macrophages, where reverse transcriptase copies its RNA into DNA that joins the host DNA, so macrophages keep making virus. It also infects and destroys helper T-lymphocytes, whose number falls steadily, leaving the person unable to fight infections such as Mycobacterium and Toxoplasma.

Are these notes enough for NEET questions on this chapter?

No. Read NCERT Chapter 7 line by line first, because NEET Biology questions closely follow the NCERT textbooks. Use these notes and the PDF for quick revision, then practise previous year questions.

Human Health and Disease NEET Notes 2027: Key Points and PDF