Human Health And Diseases Revision Notes For NEET 2023

Introduction To Human Health and Diseases:


  • Old view about health (i.e. Good humor hypothesis of health):
    • Asserted by : Early Greeks like Hippocrates as well as Indian Ayurveda system of medicine.
    • Health : State of body and mind, where there was balance of certain ‘humors’.

Early Greeks like Hippocrates

  • Persons with ‘black bile’ belonged to hot personality and would have fevers. This idea was arrived at by pure

reflective thought.

  • Disproved by : The discovery of blood circulation by William Harvey using experimental method and the demonstration of normal body temperature in persons with black bile using thermometer.

Indian Ayurveda system of medicine

  • Modern view about health:
    • Health ≠ absence of disease or physical fitness
    • Health: State of complete physical, mental and social well-being
  • Health is affected by:
  • Genetic disorders : Deficiencies with which a child is born and deficiencies / defects which the child inherits from parents from birth
  • Infections
  • Life style :
  • Food and water we take
  • Rest and exercise we give to our bodies
  • Habits that we have or lack
  • e.g. Drug and alcohol abuse also affect our health adversely.
  • Benefits of being healthy:
    • Efficiency at work ­ ® Productivity ­ ® Economic prosperity
    • Longevity ­
    • Infant and maternal mortality ¯
  • Very important to maintain good health:
    • Balanced diet
    • Personal hygiene
    • Regular exercise

Yoga :

  • Yoga has been practised since time immemorial to achieve physical and mental health.
  • Necessary for achieving good health:
    • Awareness about diseases and their effect on different bodily functions.
    • Vaccination (immunisation) against infectious diseases.
    • Proper disposal of wastes.
    • Control of vectors.
    • Maintenance of hygienic food and water resources.


  • Functioning of one or more organs or systems of the body is adversely affected.
  • Characterised by various signs and symptoms.

Classification of diseases :

  • Diseases can be broadly grouped into infectious and non-infectious :


Introduction to common diseases in humans Pathogens :

  • Pathogens are disease causing organisms (belonging to bacteria, viruses, fungi, protozoans, helminths, etc.).
  • Most parasites are therefore pathogens as they cause harm to the host by living in (or on) them.
  • Pathogens have to adapt to life within the environment of the host.

e.g. The pathogens that enter the gut must know a way of surviving in the stomach at low pH and resisting the various digestive enzymes.

How do pathogens create their pathogenicity inside our body?

Entry of pathogen into our body by various means

Multiplication of pathogen and interference with normal vital activity of our body

Morphological and functional damage to our body

Examples of infectious diseases in humans :

Type of diseaseExamples
BacterialTyphoid, Pneumonia, Dysentery, Plague, Diphtheria, Tuberculosis, Whooping cough (Pertussis), Cholera, Leprosy, etc.
ViralCommon cold, Dengue, Chikungunya, Polio or Poliomyelitis, Influenza, Measles, Chicken pox, Mumps, Rabies, SARS (Severe Acute Respiratory Syndrome), Swine flu, Covid 19, etc.
ProtozoanMalaria, Amoebiasis (Amoebic dysentery), etc.
HelminthicAscariasis, Elephantiasis (Filariasis), etc.
FungalRingworms, etc.
Types of infectious diseases
S. No.Bacterial DiseasesPathogenSymptoms & Pathogenicity
(1)Typhoid feverSalmonella typhiEnters small intestine through contaminated food and water and migrate to other organs through bloodSustained high fever (39-40°C)Weakness, constipation, stomach painHeadache, loss of appetiteIn severe cases intestinal perforation, deathWidal testMary Mallon, Nicknamed- Typhoid Mary (Carrier of typhoid)
(2)PneumoniaStreptococcus pneumoniae Haemophilus influenzaeBy droplet or aerosol infection or use of glass or utensils of infected personInfects alveoli of the lungsAlveoli get filled with fluid leading to severe problem in respirationFever with chills, cough & headacheIn severe cases lips and nails turns gray to bluish in colour
Bacterial diseases
(3)Dysentery (Shigellosis)Shigella dysenteriaeAbdominal painBlood & mucus in the stoolTransmits through faecal oral route
(4)Plague (Black death)Yersinia pestis Parasite of Xenopsylla cheopis (Rat flea)High fever, headacheEnlargement of axillary lymph nodesPneumonic (lungs)…… septa between alveoli ruptureSepticemic (blood poisoning)… Black Death
(5)DiphtheriaCorynebacterium diphtheriaeHigh grade fever, affects throatCauses suffocation (Investigation :- Schick test)
(6)Tetanus (Lock jaw)Clostridium tetaniSustained contraction of body muscles, spasms, lock jaw, unconsciousness, opisthotonus and Risus Sardonicus – Stretching of facial muscles & neck-back muscles.
Bacterial diseases
S. No.Viral DiseasesPathogenSymptoms & Pathogenicity
(1)Common coldRhino viruses (Group of viruses) (ss RNA)One of the most infectious human ailmentsTransmits through droplet resulting from cough, sneeze etc.Infect nose and respiratory passage but not the lungsNasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness
(2)Chikun- gunyaChikungunya virus (ss-RNA) (Vector :- Aedes- ageypti mosquito)Fever, joint pain, Lymphoadenopathy (enlargement of lymph nodes)
(3)Dengue fever or Break- bone-feverFlavi-arbo virus (Vector :- Aedes- ageypti mosquito)Fever, severe-frontal-headache, muscle & joint painBleeding from nose, mouth, gums
(4)Hepatitis-BHBV (ds DNA)Severe liver damage, jaundiceRecombinant DNA-vaccineTransmits-through parenteral and sexual-routeCan cross placenta
Viral diseases



Pathogen : Plasmodium (a tiny protozoan)

  • Different species of Plasmodium (P. vivax, P. malariae and P. falciparum) are responsible for different types of malaria.
  • Of these, malignant malaria caused by Plasmodium falciparum is the most serious one and can even be fatal.

Symptoms :

  • Fever  and Chills

Stages in the life cycle of Plasmodium :

  • It requires two hosts – human and mosquito – to complete its life cycle.

The female Anopheles mosquito is the vector (transmitting agent) too.

Human Health and Diseases revision notes
Life cycle of Plasmodium


  • Pathogen : Entamoeba histolytica

It is parasite in the large intestine of human.

  • Houseflies act as mechanical carriers and serve to transmit the parasite from faeces of infected person to food and food products, thereby contaminating them.

Drinking water and food contaminated by the faecal matter are the main source of infection.

Symptoms :

  • Constipation
  • Abdominal pain and cramps
  • Stool with excess mucous and blood clots

Common Diseases in Humans HELMINTHIC DISEASES


Pathogen : Ascaris (an intestinal parasite)

  • The eggs of the parasite are excreted along with the faeces of infected persons which contaminate soil, water, plants, etc.
  • A healthy person acquires this infection through contaminated water, vegetables, fruits, etc.

Symptoms :

  • Internal bleeding
  • Muscular pain
  • Fever
  • Anaemia
  • Blockage of the intestinal passage


Pathogen : Wuchereria (W. bancrofti and W. malayi) (filarial worms)

  • The pathogens are transmitted to a healthy person through the bite by the female (Culex) mosquito vectors.

Symptoms :

  • Slowly developing chronic inflammation of the organs (usually the lymphatic vessels of the lower limbs)
  • The genital organs are also often affected, resulting in gross deformities.



  • One of the most common infectious diseases in man

Pathogen : Many fungi belonging to the genera Microsporum, Trichophyton and Epidermophyton

  • Ringworms are generally acquired from soil or by using towels, clothes or even the comb of infected individuals.

Symptom :

  • Appearance of dry, scaly lesions on various parts of the body such as skin, nails and scalp
  • These lesions are accompanied by intense itching.
  • Heat and moisture help pathogenic fungi to grow, which makes them thrive in skin folds such as those in the groin or between the toes.


  • Prevention and control of food/water borne diseases such as typhoid, amoebiasis and ascariasis, etc. Maintenance of personal and public hygiene :
    • Measures for personal hygiene
      • Keeping the body clean
      • Consumption of clean drinking water, food, vegetables, fruits, etc.
    • Measures for public hygiene
      • Proper disposal of waste and excreta
      • Periodic cleaning and disinfection of water reservoirs, pools, cesspools and tanks
      • Observing standard practices of hygiene in public catering
  • Prevention and control of air borne diseases such as pneumonia and common cold, etc.
  • In addition to the previous measures, close contact with the infected persons or their belongings should be avoided.
  • Prevention and control of diseases such as malaria and filariasis, etc. that are transmitted through insect vectors

To control or eliminate the vectors and their breeding places, which can be achieved by :

  • Avoiding stagnation of water in and around residential areas
  • Regular cleaning of household coolers
  • Use of mosquito nets
  • Introducing fishes like Gambusia in ponds that feed on mosquito larvae
  • Spraying of insecticides in ditches, drainage areas and swamps, etc
  • Providing doors and windows with wire mesh to prevent the entry of mosquitoes

Such precautions have become more important especially in the light of recent widespread incidences of the vector- borne (Aedes mosquitoes) diseases like dengue and chikungunya in many parts of India.

Human health and diseases revision notes free download pdf

The advancements made in biological science which have armed us to effectively deal with many infectious diseases

  • Discovery of antibiotics and various other drugs has also enabled us to effectively treat infectious diseases.
  • The use of vaccines and immunisation programmes have enabled us to completely eradicate a deadly disease like smallpox, and to control other infectious diseases like polio, diphtheria, pneumonia and tetanus to a large extent.
  • Biotechnology is at the verge of making available newer and safer vaccines.


Introduction to immunity:

Everyday we are exposed to large number of infectious agents. However, only a few of these exposures result in disease. Why?

  • Overall ability of the host to fight the disease-causing organisms or resistance of the body against a disease is called immunity.
  • Immunity is conferred by the immune system.

Classification of immunity

  • Immunity is of two types :
Innate ImmunityAcquired Immunity
Pathogen non-specific type of defence
Present at the time of birth (Inborn/Congenital)
Not characterised by memory
Found in plants and animals both
It includes monocytes, neutrophils, NK cells and macrophages
Pathogen specific type of defence
Acquired during life (Adaptive)
Characterised by memory
Found in higher vertebrates only
It    includes    T-lymphocytes    and B- lymphocytes
Innate immunity vs Acquired immunity

Innate immunity:

  • Innate immunity is accomplished by providing different types of barriers to the entry of the foreign agents into our body.
  • Innate immunity consists of four types of barriers :
    • Physical barriers
    • Physiological barriers
    • Cellular barriers
    • Cytokine barriers
  • Physical barriers of innate immunity

Following structures are included in these barriers :

  • SkinSkin on our body is the main barrier which prevents entry of the micro-organisms into our body.Outermost layer of skin (Stratum corneum) is dead, so the bacteria do not grow or enter into it.

pH of skin is acidic (3-5) in nature, destroys the bacteria.

  • MucosaMucus coating of epithelium lining of the respiratory, gastrointestinal and urogenital tracts also act as physical barriers for microbes entering our body.Mucosa contain mucosal cells and cilia.Mucous secreted by mucosal cells and cilia help in trapping and propelling the microbes respectively.
  • Physiological barriers of innate immunity
  • Fever, acidic pH of various body parts (like oral cavity, stomach and vagina) and secretions containing lysozyme enzyme (like tears, sebum) are included in this type of barrier.
  • Acid in the stomach, saliva in the mouth, tears from eyes all prevent microbial growth.
  • Some physiological processes of body create adverse environment for growth of bacteria.

Critical Thinking

In response to pathogenic infection, the total count of WBC in body increases. Why?

Innate Immunity:

  • Cellular barrier of innate immunity
  • There is involvement of two types of cells :
    • Phagocytic Cells
    • These cells perform phagocytosis.
    • Examples of phagocytic cells are :
    • In blood : Polymorpho-nuclear leukocytes (PMNL- neutrophils), Monocytes
    • In tissues : Macrophages

Note : Monocytes are liberated at the site of infection and later converted into macrophages.

  • Non-Phagocytic Cells
    • These cells do not perform phagocytosis.
    • Example of non-phagocytic cells is Natural Killer cell or NK cell.
  • NK cell kills abnormal cell by creating perforin lined pores in the plasma membrane. Water enters through these pores causing swelling and bursting of the abnormal cell.
  • Cytokine barrier of innate immunity
  • It includes interferons.
  • Interferons are antiviral proteins, secreted by virus infected cells.
  • Interferons are chemically glycoproteins, each molecule consisting of 270 amino acids.
  • Interferons protect non-infected cells from further viral infection by stimulating the adjacent normal cells to produce Translational Inhibiting Protein (T.I.P.).
  • Interferons are not virus specific, but are species specific.


  • AIDS is a chronic, potentially life-threatening condition caused by the human immunodeficiency virus (HIV).
  • HIV attacks the body’s immune system, making it difficult for the body to fight off infections and diseases.
  • AIDS is the most advanced stage of HIV infection.
  • Symptoms of AIDS can vary depending on the individual, but may include:
    • Persistent fatigue
    • Fever
    • Night sweats
    • Weight loss
    • Diarrhea
    • Swollen lymph nodes
    • Oral thrush
    • Pneumonia
    • Skin infections
    • Cancer
  • There is no cure for AIDS, but antiretroviral therapy (ART) can help control the virus and prevent progression to AIDS.
  • ART is a lifelong treatment, but it can help people with HIV live long, healthy lives.

The HIV virus

The human immunodeficiency virus (HIV) is a virus that attacks the body’s immune system. The virus is spread through contact with blood, semen, vaginal fluids, and breast milk. HIV can be spread through sexual contact, sharing needles, and from mother to child during pregnancy, childbirth, or breastfeeding.

HIV diagnosis

There are several ways to diagnose HIV infection. The most common test is a blood test that looks for antibodies to HIV. Antibodies are proteins that the body produces in response to infection. If you have HIV, your body will produce antibodies to the virus.

Other tests that can be used to diagnose HIV infection include:

  • A rapid HIV test, which can give results in minutes
  • A viral load test, which measures the amount of HIV in the blood
  • A CD4 count test, which measures the number of CD4 cells in the blood. CD4 cells are a type of white blood cell that help the body fight infection.

Stages of AIDS

If left untreated, HIV infection can progress to AIDS. AIDS is the most advanced stage of HIV infection. People with AIDS have severely weakened immune systems and are at high risk for opportunistic infections. Opportunistic infections are infections that are usually not a problem for people with healthy immune systems.

There are three stages of HIV infection:

  • Acute HIV infection: This is the first stage of HIV infection. It usually occurs within 2 to 4 weeks after infection. Symptoms of acute HIV infection can be similar to the flu, and may include fever, fatigue, rash, swollen lymph nodes, sore throat, and mouth sores.
  • Chronic HIV infection: This is the second stage of HIV infection. It can last for many years without symptoms. However, the virus is still active in the body and can be transmitted to others.
  • AIDS: This is the most advanced stage of HIV infection. People with AIDS have severely weakened immune systems and are at high risk for opportunistic infections.

Treatment for HIV

There is no cure for HIV, but there are effective treatments that can help people with HIV live long, healthy lives. Treatment for HIV involves taking antiretroviral therapy (ART). ART is a combination of medications that work together to suppress the virus. When taken as prescribed, ART can reduce the amount of HIV in the blood to undetectable levels. This means that the virus is not detectable by standard laboratory tests and cannot be transmitted to others.

  • AIDS can be prevented by:
    • Practicing safe sex
    • Using clean needles
    • Getting tested for HIV
    • Getting vaccinated against hepatitis B

Here are some additional resources about AIDS:


Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in bowel movements. While these symptoms may indicate cancer, they may have other causes. Over 100 types of cancers affect humans.

Tobacco use is the cause of about 22% of cancer deaths. Another 10% is due to obesity, a poor diet, lack of physical activity, and excessive drinking of alcohol. Some cancers are caused by infections, such as hepatitis B, hepatitis C, human papillomavirus (HPV), and Epstein–Barr virus (EBV). Other factors include exposure to ionizing radiation and environmental pollutants.

Age is the most important risk factor for most cancers. The risk of developing cancer increases with age. Other risk factors vary by cancer type. For example, the risk of breast cancer is higher in women who have a family history of the disease or who have certain genetic mutations.

The symptoms of cancer vary depending on the type of cancer and the stage of the disease. Some common symptoms include:

  • A lump or mass
  • Unexplained weight loss
  • Persistent cough
  • Blood in the urine or stool
  • Pain
  • Fatigue
  • Fever
  • Changes in bowel or bladder habits
  • Changes in skin
  • Sores that do not heal

If you have any of these symptoms, it is important to see a doctor right away. Early diagnosis and treatment are important for improving the chances of survival for many types of cancer.

There are a number of things that can be done to reduce the risk of cancer, including:

  • Not smoking
  • Eating a healthy diet
  • Exercising regularly
  • Maintaining a healthy weight
  • Limiting alcohol intake
  • Getting vaccinated against certain infections, such as HPV and hepatitis B
  • Avoiding exposure to ionizing radiation and environmental pollutants

If you are concerned about your risk of cancer, talk to your doctor. There are things you can do to reduce your risk, such as getting screened for certain types of cancer.

The diagnosis of cancer is usually made through a combination of tests, including:

  • Physical examination
  • Blood tests
  • Imaging tests, such as X-rays, CT scans, and MRI scans
  • Biopsy, which is the removal of a small piece of tissue for examination under a microscope

The treatment of cancer depends on the type of cancer, the stage of the disease, and the patient’s overall health. Treatment options may include surgery, radiation therapy, chemotherapy, targeted therapy, and immunotherapy.

In some cases, cancer can be prevented by avoiding exposure to risk factors. For example, smoking is a major risk factor for lung cancer, so quitting smoking can help to prevent lung cancer. Other risk factors, such as obesity and exposure to certain infections, can be reduced by making lifestyle changes.

Cancer is a complex disease with many causes and risk factors. There is no one-size-fits-all approach to prevention or treatment. However, there are things that people can do to reduce their risk of cancer and improve their chances of survival if they do develop the disease.

Here are some additional resources about cancer:

Also Read: 1. The Living World: Revision Notes for NEET


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