Diseases in Humans Notes for SSC CGL, CHSL and Railways

Diseases in Humans Notes for SSC CGL, CHSL and Railways


A disease is a particular abnormal condition that negatively affects the structure or function of part or all of an organism, and that is not due to any external injury.

DPT (Diphtheria, Pertussis and Tetanus) is a class of combination vaccines against three infectious diseases in humans.

Table of Contents

Various Disease and their Agents

Agent Diseases
Bacteria Diphtheria, Gonorrhea, Cholera, Leprosy, Typhoid, Tetanus, TB, Plague, Whooping Cough, Pneumonia
Virus Chicken Pox, Small Pox, Measles, Mumps, HIV/AIDS, Yellow fever, Influenza, Dengue Fever, Rabies, Polio-meritis
Protozoans Malaria, Sleeping Sickness, Kala-azar, Leishmaniasis, Amoebic dysentery
Fungus Ringworm, Jock itch, Athlete’s foot

Food Poisoning is caused by Bacteria (Campylobacter jejuni, Clostridium perfringens, Salmonella typhimurium and Escherichia coli) or by Enterotoxins (Clostridium botulinum, Clostridium perfringens, Bacillus cereus) etc.

Viral Diseases

Disease Virus Description
Rabies Rabies virus (Rhabdoviridae family) Bite or scratch of an animal
Small pox Variola Virus Globally eradicated in 1980
Chicken pox Varicella-zoster Virus Spreads easily, Vaccine Available
AIDS(Acquired Immuno Deficiency Syndrome) HIV (human immunodeficiency virus) STD, Virus destroys Lymphocytes
Dengue (breakbone fever) Dengue virus Mostly by Aedes aegypti
Mumps Mumps virus Spreads through infected saliva, causes inflammation of Parotid gland.
Measles Rubeola virus Spreads easily from infected ones.
Yellow Fever Flavivirus By the bite of Aedes aegypti
Influenza (The Flu) Influenzavirus (Type A, B and C) Spreads easily, Annual vaccine available

BCG (Bacillus Calmette–Guérin) is a vaccine primarily used against tuberculosis.

Bacterial Diseases

Disease Bacteria Description
Typhoid Salmonella Typhii Spreads through contaminated food and water
Tetanus (lockjaw) Clostridium tetani Affects nerves, DPT vaccine available.
Perussis (Whooping Cough) Bordetella pertussis These bacteria attach to the cilia that line part of the upper respiratory system.
Diptheria Corynebacterium diphtheriae Transmitted easily, DPT vaccine
Cholera Vibrio cholerae Fatal, if not treated immediately.
Pneumonia Streptococcus pneumoniae Pneumonia causes inflammation in the air sacs in your lungs, which are called alveoli.
Gonorrhea Neisseria gonorrhoeae STD
Syphilis Treponema pallidum STD
Tuberculosis (TB) Mycobacterium tuberculosis Transmitted through airborne droplets or saliva & affects the entire body part majorly Lungs & Bones.
Leprosy (Hansen’s disease) Mycobacterium Leprae Chronic, curable, infectious – causes skin lesions and nerve damage
Plague Yersinia pestis Spreads via rats and airborne droplets. Symptoms include fever, weakness & headache

Protozoan Diseases

Disease Protozoa Description
African trypanosomiasis (Sleeping sickness) Trypanosoma brucei Transmitted through the bite of Tse-Tse fly
Malaria Plasmodium Transmitted through the bite of Female Anopheles mosquito.
Amoebiasis (Amoebic dysentery) Entamoeba histolytica Spreads through contaminated food or water
Leishmaniasis (Kala azar) Leishmania AKA Black Fever, spread by sandfly bites

Fungal Diseases

Disease Description
Ringworm (dermatophytosis or tinea) Spread by skin-to-skin contact or by touching an infected animal or object
Athlete’s foot (tinea pedis) Scaly rash that usually causes itching, stinging and burning.
Jock itch (tinea cruris) Fungal infection in the skin of the genitals, inner thighs and buttocks. Causes an itchy, red, often ring-shaped rash.

Worm Diseases

Disease Name of Fungi Description
Filariasis (Elephantiasis) Filarial Worm Spread by infected mosquitoes
Enterobiasis Pinworm Spread by swallowing or inhaling the tiny eggs of the pinworm

Genetic Disorders

Disorder Cause Description
Down syndrome A genetic chromosome 21 disorder causing developmental and intellectual delays. Wide range of development delays and physical disabilities.
Hemophilia A disorder in which blood doesn’t clot normally. Symptoms include many large or deep bruises, joint pain and swelling, unexplained bleeding and blood in urine or stool.
Thalassemia A blood disorder involving lower-than-normal amounts of an oxygen-carrying protein. Symptoms include fatigue, weakness, paleness and slow growth.
Cystic fibrosis An inherited life-threatening disorder that damages the lungs and digestive system. Cystic fibrosis affects the cells that produce mucus, sweat and digestive juices. It causes these fluids to become thick and sticky. They then plug up tubes, ducts and passageways.


A disease in which abnormal cells divide uncontrollably and destroy body tissue. Treatment may involve chemotherapy, medication, radiation therapy and rarely stem-cell transplant.

Diesease Cause Description
Breast cancer A cancer that forms in the cells of the breasts. Symptoms: lump in the breast, bloody discharge from the nipple and changes in the shape or texture of the nipple or breast.
Prostate cancer A cancer in a man’s prostate, a small walnut-sized gland that produces seminal fluid. Symptoms: difficulty with urination, but sometimes there are no symptoms at all.
Lung cancer A cancer that begins in the lungs and most often occurs in people who smoke. Symptoms: cough (often with blood), chest pain, wheezing and weight loss.
Lymphoma (Lymphatic Cancer) A cancer of the lymphatic system. Symptoms: enlarged lymph nodes, fatigue and weight loss
Melanoma (Skin Cancer) The most serious type of skin cancer. Symptoms: new, unusual growth or a change in an existing mole
Leukemia (Blood Cancer) A cancer of blood-forming tissues, hindering the body’s ability to fight infection. Many types exist such as acute lymphoblastic leukaemia, acute myeloid leukaemia and chronic lymphocytic leukaemia.
Colon cancer A cancer of the colon or rectum, located at the digestive tract’s lower end. These often have no symptoms but can be detected by screening.


A group of diseases that result in too much sugar in the blood (high blood glucose).

Type Cause Description
Type 2 diabetes (adult onset diabetes) A chronic condition that affects the way the body processes blood sugar (glucose). With type 2 diabetes, the body either doesn’t produce enough insulin, or it resists insulin
Type 1 diabetes (juvenile diabetes) A chronic condition in which the pancreas produces little or no insulin. Symptoms: increased thirst, frequent urination, hunger, fatigue and blurred vision.
Prediabetes A condition in which blood sugar is high, but not high enough to be type 2 diabetes. Without intervention, it’s likely to become type 2 diabetes within 10 years.
Gestational diabetes A form of high blood sugar affecting pregnant women. Those who develop gestational diabetes are at higher risk of developing type 2 diabetes later in life.

Nutritional Deficiency Diseases

Malnutrition is a condition that results from eating a diet in which one or more nutrients are either not enough or are too much such that the diet causes health problems.

Diease Cause Effect Nutrition Sources
Rickets Deficiency of Vit D along with Ca & P weak and soft bones, bowed legs and bone deformities Fish, fortified dairy products, liver, oil and sunlight
Pellagra Deficiency of Vit B3 (Niacin) 3Ds (dementia, diarrhea and dermatitis) Tuna, whole grains, peanuts, mushrooms, chicken
Scurvy Deficiency of Vit C (ascorbic acid) Scurvy basically inhibits the production of collagen in the body which is the structural protein that connects the tissues. Decaying of the skin and gums, abnormal formation of teeth and bones, delay or inability to heal wounds and bleeding. Citrus fruits like oranges, lemon, strawberry etc and broccoli
Beri Beri Deficiency of Vit B1 (thiamine) Altered muscle coordination, nerve degeneration and cardiovascular problems Meat, eggs, whole grains, dried beans
Xerophthalmia (Night Blindness) Deficiency of Vit A Blindness due to poor growth, dryness and keratinisation of epithelial tissue or chronic eye infection Carrots, green and leafy vegetables, cantaloupes
Goitre Deficiency of Iodine Enlarged thyroid glands causing hypothyroidism, poor growth and development of infants in childhood, cretinism and even mental retardation Iodised salt and saltwater fish
Anaemia Deficiency of Iron Decrease in the red blood cell count or hemoglobin in the body, resulting in fatigue, weakness, dyspnoea and paleness of the body. Squashes, nuts, tofu, bran
Kwashiorkor Deficiency of protein & energy Anorexia, an enlarged liver, irritability and ulcerating dermatoses Eggs, lentils, rice
Depression Deficiency of Vit B7 (biotin) depression, hair loss, rashes and mental issues Squashes, nuts, tofu, bran
Osteoporosis Deficiency of Vit D & Ca Unhealthy, soft and brittle bones that are prone to fractures and defects in the spine structure Bananas, spinach, milk, okra, soy and sunlight

Important Scientists

  1. Lois Pasteur: Renowned for his discoveries of the principles of vaccination, microbial fermentation and pasteurization. Discovered first vaccines for rabies and anthrax.
  2. Robert Koch (founder of modern bacteriology): Identified the causative agents of tuberculosis, cholera, and anthrax and gave experimental support for the concept of infectious disease. For his research on tuberculosis, Koch received the Nobel Prize in Physiology or Medicine in 1905.
  3. Edward Jenner (father of immunology): Pioneer of smallpox vaccine, the world’s first vaccine.
  4. Sir Alexander Fleming: Best-known discoveries are the enzyme lysozyme in 1923 and the world’s first antibiotic substance benzylpenicillin (Penicillin G) from the mould Penicillium notatum in 1928, for which he shared the Nobel Prize in Physiology or Medicine in 1945 with Howard Florey and Ernst Boris Chain.
  5. Antonie van Leeuwenhoek (Father of Microbiology): Microscopic discovery of microorganisms (animalcule)

Both Antonie van Leeuwenhoek and Louis Pasteur are known as father of microbiology.

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