Human Diseases

Diseases may be defined as a disorder in the physical, physiological, psychological, or social state of a person caused by nutritional deficiency, physiological disorder, genetic disorder, pathogen, or any other reason.

Classification of Diseases 

Diseases may be classified as Congenital diseases and Acquired diseases.

Congenital disease – These diseases are present from birth (e.g. hole in the heart in infants). They are caused by some genetic abnormalities or metabolic disorders or malfunctioning of an organ.

Acquired diseases These diseases may occur after birth caused by many factors. Acquired diseases may be classified as-

  • Infectious diseases
  • Degenerative diseases
  • Deficiency diseases
  • Cancer

Infectious diseases: This type of disease can be transmitted from a diseased person to a healthy person e.g. measles.

Degenerative diseases: This type of disease is caused by the malfunction of some vital organs of the body e.g. heart failure or kidney failure.

Deficiency diseases: These are caused by nutritional deficiencies like minerals or vitamins in the diet e.g. Anaemia (Fe), Beri- Beri (vitamin B).

Diseases in humans due to deficiency of vitamins are listed below:
vitamin Sources Deficiency symptom
Fat-soluble vitamins  
Vitamin A( Retinol) Milk, cheese, butter, eggs cod liver oil, spinach, etc. Night blindness. Cannot see in dim light(night blindness)
Vitamin D (Calciferol) Milk, cheese egg yolk, cod liver oil, sunlight. Rickets in children Failure of growing bones, softening of bones seems bow legs, pigeon chest
Vitamin E (Tocopherol) Grains, vegetable oil, green leafy vegetables, etc. Problems in the reproduction of males and females Sterility in males, miscarriage, or other problems in females.
Vitamin K (phylloquinone) Green leafy vegetables, soybean,  tomatoes. Hemorrhage, (Don’t clot of blood on average time ) Delayed blood clotting
Water-soluble vitamins
Vitamin B1 (Thiamine) Yeast, milk, cheese, leafy vegetables, meat, etc. Beri-beri Pain in hands and feet. Oedema.
Vitamin B2 (Riboflavin) Milk, liver whole grains, eggs, peas, etc. Ariboflavinosis cracks in the skin at the corners of the mouth, fissures of the lips, etc.
Vitamin B3 (Niacin) Fish, eggs, legumes whole grains, peanuts, beans, etc. Pellagra Dermatitis, diarrhea, dementia
Vitamin B12 (cyanocobalamin) cheese; milk; Liver; fish; etc. Pernicious anemia Paleness of skin, the problem in breathing.
Vitamin C (Ascorbic acid) Amla, cabbage, lemon, orange, and other citrus fruits. Scurvy Bleeding Gums, pain in joints, weakness
Some diseases are caused by a deficiency of minerals

Minerals play a vital role in our life, as they help in growth, circulation and so many functions. The deficiency of these minerals also causes diseases.

List of some common human diseases caused by mineral deficiencies:

Minerals Functions Food sources Deficiency
Calcium Formation of bones and teeth, necessary for nerve and muscles. Milk, dairy products, green leafy vegetable cereals, etc. Rickets, Osteomalacia, Degradation of teeth
Iron Formation of hemoglobin Green, vegetables, spinach, jaggery, etc. Anemia, loss of appetite
Phosphorus Formation of bones and teeth Milk; Cereals, Green leafy vegetables, Nuts, bajra, etc. Softening of bones
Iodine Metabolic control of thyroxine hormone, mental ability Iodized salt, seafood, green leafy vegetable, etc. Enlargement of the thyroid gland called Goitre
Sodium and Potassium Maintenance of water balance, and conduction of nerve impulses. Common salt, eggs, spinach; pulses, etc. High blood pressure. Balance disturbance.
PEM caused by Malnutrition

Protein-energy malnutrition (PEM) A number of children in the age group of 1-5 years suffering PEM, is caused by two reasons:

  • Lack of proteins or carbohydrates or both in the diet.
  • Excess intake of carbohydrates than proteins.
  • It causes two diseases Marasmus, and Kwashiorkor
PEM malnutrition diseases

Cancer: This is an abnormal, uncontrolled, and unwanted growth of cells. e.g. Liver cirrhosis, Brain tumors, etc.

Acquired diseases can be studied under two categories

  • Communicable diseases These diseases transmit from an infected person to a healthy person.
  • Non-communicable diseases These diseases do not transmit from an affected person to a healthy person
Modes of communicable diseases:

Modes by which the Spread of Communicable Diseases takes place-

Communicable diseases can spread from the infected person to a healthy person in the following ways.

Direct transmission

The pathogens of diseases infect a healthy person directly without an intermediate agent. It can take place by various means such as-

  • Direct contact between the infected person and the healthy person: Diseases like smallpox, chickenpox, syphilis, and gonorrhea spread via direct contact.
  • Droplet infection: The infected person’s tiny droplets of mucous by coughing, sneezing, or spitting. These droplets may contain the pathogen. By inhaling the air containing the droplets, a healthy person may get the infection. Diseases like the common cold, pneumonia, influenza, measles, tuberculosis, and whooping cough spread through droplet infection.
  • Contact with soil: contaminated soil with disease-causing organisms or viruses.
  • Animal bite: Viruses of rabies are introduced through the wound caused by the bite of rabies animals, especially dogs.

Indirect Transmission

certain diseases in humans are caused by some pathogens which come indirectly into the body by some intermediate carrier. For example- By vectors such as houseflies, mosquitoes, and cockroaches

Some Common human communicable diseases

Common human diseases caused by viruses

  • Chickenpox-
    • Pathogen: Chickenpox virus (varicella)
    • Incubation period: 12-20 days
    • Symptoms- fever, headache, loss of appetite, Dark red colored rash on the back and chest which spreads on the whole body.
    • Prevention: vaccine
  • Measles
    • Type of infectious agent: Virus
    • Prevention factors: MMR vaccine
    • symptom- Common cold, small white patches appear in the mouth and throat, the appearance of rashes on the body.
    • Prevention- The patient should be kept in isolation, Cleanliness must have maintained, and Antibiotics check only the secondary infections which can easily recur.
  • Poliomyelitis-
    • Pathogen: Polio Virus
    • Mode of transmission: Viruses enter the body through contaminated food or water.
    • Incubation period: 7-14 days
    • Symptoms- It damages the brain and nerves and causes infantile paralysis, and stiffness of the neck, fever, loss of head support can be found.
    • Prevention- Polio vaccine drop (oral polio vaccine, OPV) is given to children at certain intervals.

***Pulse polio program is organized in our country by the government to give polio vaccine to children.

  • Rabies (hydrophobia)-
    • Pathogen: Rabies virus
    • Mode of Transmission: Biting by a dog carrying the rabies virus.
    • Symptoms- Severe headache and high fever, Painful contraction found in muscles of throat and chest, fear of water lead to death.
    • Prevention- Compulsory immunization of dogs, the killing of rabid animals, Anti-rabies injections, or oral doses must give to the person bitten by a rabid animal.
  • Hepatitis-
    • Pathogen: Hepatitis B virus
    • Mode of Transmission: Mainly transmits through contaminated water.
    • Incubation Period: Generally, 15-160 days.
    • Symptoms- Pain in the body, Loss of appetite and nausea, Eyes and skin become yellowish, urine deep yellow in color (due to bile pigments). Enlargement in the liver was found.
    • Prevention and Cure- Hepatitis B vaccine should be given to an infected person, simple and healthy food that must not be oily.
  • Influenza (flu)-
    • Pathogen– Virus
    • Symptoms– fever normally 100 ° F to 103° F in adults and even higher in children with infection in the respiratory tract. Symptoms such as cough, sore throat, running nose, headache, pain in the muscles, and extreme fatigue.
    • Prevention and cure– The influenza vaccine should be given to those who are at high risk for complications with chronic diseases of the heart, lungs, or kidneys, diabetes, or severe forms of anemia. Advice from the doctor should be taken.
  • Dengue- Dengue is an acute fever caused by the virus. It is of two types:
    • Dengue fever– main characteristics of this fever are sudden high fever, severe headache, and pain in the muscles, and joints.
    • Dengue hemorrhagic fever– It is an acute infectious viral disease. It is an advanced stage of dengue fever. It is characterized by fever during the initial phase and other symptoms like headache, pain in the eye, joint pain, and muscle pain, followed by signs of bleeding, red tiny spots on the skin, and bleeding from the nose and gums
    • Pathogen– a bite of an infected Aedes Aegypti mosquito
Ades mosquito causes very common disease Dengue
  • Incubation period– After a bite of a mosquito carrying the dengue virus the symptoms start on average 4 to 6 days, with a range of 3 to 14 days.
    • Symptoms- Sudden onset of high fever, generally 104-105 °F (40 °C), which may last 4-5 days. Severe headache mostly in the forehead, Nausea, or vomiting. After all, if treatment is not done, then Dengue hemorrhagic fever occurs. In hemorrhagic dengue rashes on the skin, Bleeding from the nose, mouth, or internal organs, Black stools due to internal bleeding, Excessive thirst, Pale, cold skin, and weakness are found.
    • Prevention- Avoid water stagnation for more than 72 hours by which the breeding of mosquitoes can be stopped there. Use mosquito repellents and long-sleeved clothes to curtail exposure. Use mosquito nets, also during the daytime. After all these preventions the infected person should go to a medical consultancy.

*** We will know about other major pathogens and diseases in the next blog- Common Human Diseases pathogenic

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