HUMAN DISEASES: INTRODUCTION

COMMUNICABLE AND NON-COMMUNICABLE DISEASES

· Health is defined as the state of complete physical, mental and social well-being of an organism and not only absence of disease or physical fitness.

· Health and its Importance
· Meaning of health differs from person to person.

· It may mean a muscular body to a wrestler and a slim body to a dancer.
· Good health not only means being disease-free and physically fit but it refers to good mental health and also emotional stability.

· Actually, physical, mental and emotional health, are all interrelated.
· Health is maintained and improved not only through the advancement and application of the health science, but also through the efforts and intelligent lifestyle of the individuals as well as the society. Achieving health and remaining healthy is an ongoing process.
· Health not only affects the individuals but also the community in which we live. Good health enables a person to perform at his or her best as an individual, as families, as a community and as a nation.

· It is often said, “healthy people make a happy community”.
· When people are healthy, they are more efficient at work. This increases productivity and brings economic prosperity.

· It also brings longevity to people and reduces infant and maternal mortality.

Ways to maintain Good Health
· There is a saying “A sound physical health is the first and the foremost important requisite for the performance of one’s duty in one’s life”.

· It is important to know the following to maintain good health.
· Balanced diet: A balanced diet containing different types of food in the right quantity and proportion is important to provide energy for daily needs and growth, development and maintenance of the body.

· Personal hygiene: It is one of the most effective ways to protect oneself and others from illness. It includes personal cleanliness and maintenance of the cleanliness in the surrounding. The person should be careful to wash hands before eating and take care of one’s nails, hair, teeth, eyes and general body hygiene.

· Regular exercise: It is necessary to keep the body and mind fit. Exercise may vary with age, physical condition and nature of work, but is nevertheless essential to keep the body in good shape. Yoga has been practised to achieve physical and mental health.

· Relaxation and regular sleeps are relief or diversion from the work. Relaxation could be through yoga, meditation, listening to music, reading, gardening, walking or anything into which a person can indulge himself completely forgetting his work. Regular sleep is essential to revitalize the body after work. It may depend on age, health and nature of work.

· Awareness about the disease and its effect on different body functions, vaccination against infectious diseases, proper disposal of wastes, control of vectors and maintenance of hygienic food and water resources are necessary to achieve good health.

· Disease is an abnormal condition of an organism that impairs bodily functions. It is the dis-ease or absence of comfort in the body.
· Symptom is a change in health experienced by a patient Example: Fatigue, Nausea etc.
· Signs are clinically recognizable features discovered by a physician indicating the nature of diseases. Example: elevated blood pressure, abnormal appearance of retina etc.
· Syndrome is the association of several clinically recognizable features, signs, symptoms or characteristics which occur together so that presence of one feature alters the physician to the presence of others.

Types of Diseases

· Diseases are broadly classified into two types.

· They are Acquired and Congenital.

A. Acquired diseases:

· Diseases developed afterbirths are called acquired diseases.

· These are of further 2 types- communicable and non-communicable.

a. Communicable diseases (Infectious diseases)
· Those diseases which can be transferred from an infected person to a healthy person through different media like air, water, food and direct contact are called communicable diseases or infectious diseases.

· Example: Typhoid, TB, AIDS, Kala-azar etc.

b. Non-communicable diseases (Non-infectious diseases)
· Those diseases which do not spread to others and remain confined to a person are called non-communicable diseases or non-infectious diseases.

· They are caused by agents other than pathogens.

· They may be of the following types:
i. Deficiency diseases: deficiency of nutrients, vitamins, hormones, minerals. Examples: Kwashiorkor, Marasmus, Goitre, Diabetes, Beri-Beri etc.

ii. Degenerative changes: malfunctioning of some organs or due to old age.

· Examples: Heart diseases, Brain diseases (epilepsy) etc.

iii. Allergies: caused when the body becomes hypersensitive to certain foreign substances.

· Example: Rhinitis, Hay fever, Asthma etc.

iv. Addictions: due to drug abuse, alcohol and tobacco.

· Example: Liver cirrhosis.

v. Mental disorders: due to depression, anxiety, mental disability.

vi. Cancer: due to uncontrolled growth of tissues.

· Example: Breast cancer, Lung cancer etc.

B. Congenital diseases
· These diseases have already been contracted at birth.

· They are of TWO basic types.
a. Hereditary or genetic diseases
· These can be caused by:
i. Single gene mutation

· Example: alkaptonuria, phenylketonuria, sickle-cell anaemia, haemophilia, colour blindness etc.

ii. Chromosomal aberrations

· Example: Down’s syndrome, Turner’s syndrome, Klinefelter’s syndrome etc.

b. Diseases due to environmental factors
i. Transplacental transmission

· Example: Measles, Syphilis etc.
ii. Developmental defects

· Example: Cleft palate, Hare lip etc.

· The gene and chromosomal induced congenital defects are transmitted to the children whereas the environmentally caused abnormalities are not.

Communicable diseases	Non-communicable diseases
These are caused by pathogens or causative agents like bacteria, viruses, protozoan, helminth, fungus etc.	These are not caused by pathogens or causative agents.
These diseases are transmitted from one person to another.	These diseases are not transmitted from one person to another.
Mode of transmission is present.	No mode of transmission.
Typhoid, Cholera, Tuberculosis, AIDS, STDS are examples of communicable diseases.	Cancer, Heart diseases, blood pressure, Diabetes are examples of non-communicable diseases.
Factors are lack of sanitation and spreading of vectors (insects) etc.	Factors are overnutrition, idle habits, worried and lack of exercise.

Classification of Communicable Diseases

· They are classified on the basis of causative agents.
1. Bacterial Diseases: Diseases caused by bacteria.

· Example: Cholera, Typhoid, Tuberculosis (TB), Meningitis, Syphilis etc.

2. Viral Diseases: Diseases caused by viruses.

· Example: AIDS, Bird flu, Influenza, Chickenpox, Smallpox, Common cold, Measles, Polio, Rabies, Yellow fever etc.

3. Protozoan Diseases: Diseases caused by protozoans.

· Example: Malaria, Kala-azar or Leishmaniasis, Amoebic dysentery or Entamoebiasis, Trichomoniasis, Giardiasis, Trypanosomiasis or Sleeping sickness etc.

4. Helminth Diseases: Diseases caused by flatworms and roundworms.

· Example: Fasciolopsis or Liver-rot, Schistosomiasis, Ascariasis, Ancylostomiasis, Taeniasis, Filariasis etc.

5. Fungal Diseases: Diseases caused by fungi.

· Example: Ringworm, Athlete’s foot, Aspergillosis, Candidiasis etc.

6. Rickettsial Diseases: Diseases caused by Rickettsia parasite

· Example: Q fever, Typhus fever, Trench fever, Rocky Mountain spotted fever etc.

7. Arthropod Diseases: Disease caused by arthropods

· Example: Scabies, Plague etc

The Way Pathogens cause Diseases
· Pathogens cause diseases in two ways: tissue damage and toxin secretion.

a. Tissue damage:

· In this case, pathogens cause damage to tissues.

· For example, the bacteria responsible for tuberculosis damage cells and cause lesions in the lungs.

· Blood oozes from the lesions into the air sacs, leading to haemorrhages.

· The bacteria are responsible for meningitis attacking the meninges, covering the brain.

· The rabies virus destroys brain tissue and poliovirus damages motor nerve cells in the spinal cord.

b. Toxin secretion:

· Many microbes produce powerful poisons, called toxins, which cause diseases.
· Toxins are of two types:
i. Exotoxins:

· These toxins are released as soon as they are produced.

· The diseases brought about by exotoxins include tetanus, diphtheria, scarlet fever and botulism (food poisoning).

ii. Endotoxins:

· These are retained in the bacterial cell and released when bacteria die and disintegrate.

· The diseases caused by endotoxins include typhoid fever, cholera, bubonic plague and dysentery.

MODE OF TRANSMISSION OF COMMUNICABLE DISEASE

· The communicable disease is transmitted from an infected person to a healthy person through two different methods:

1. Direct Method:

· Disease which is transmitted directly or without intermediate agents.

· It occurs in many ways:

a. Contact with infected ones: Chickenpox, Smallpox, Syphilis etc.

b. Droplet infection: Sneezing, coughing, spitting, talking, Example: Diptheria, Influenza, Common cold, Measles, Tuberculosis, Pneumonia etc.

c. Contact with soil: Example: Bacteria responsible for tetanus.
d. Animal bites: Example: Rabies.
e. Through placenta: Example: AIDS, Bacteria of Syphilis, German Measles etc.

2. Indirect transmissions:

· The diseases which are indirectly transmitted from infected person to healthy person through various media called indirect transmissions.

· In this case, pathogens are carried through some intermediate agents.

· It occurs in the following ways.
a. By air: The micro-organisms or pathogen transmitted from infected to a healthy person through air or droplets (while sneezing, coughing, talking etc.)

· Eg. Epidemic typhus, T.B., Common cold etc.

b. Water: The pathogens which are transmitted through contaminated water

· Example: Cholera, Typhoid, Amoebic dysentery, Diarrhoea, Jaundice etc.

c. Arthropod vectors: Pathogens transmitted by arthropods,

· Example: Housefly-Typhoid, Cholera, Dysentery; Anopheles mosquito (Malaria), Sandfly (Kala-azar), Culex mosquito (Filariasis), Tsetse fly (African sleeping sickness), Bed bug (Trench fever), Rat flea (Bubonic Plague) etc.

Terms Related to Diseases

1) Parasite or Pathogen: an infective agent that causes disease in another animal. Protozoan, fungi, helminth, bacteria, virus.

2) Host: Living organism through which parasites derive their nourishment and get shelter.

a. Primary or Definitive Host: Host where the parasite completes sexual reproduction,

· Example: Man is the definitive host for all the parasites except malaria and hydatid disease.
b. Secondary or Intermediate host: Host where parasite completes the asexual reproduction.

· Example: all invertebrates are the intermediate hosts except the Anopheles mosquito in malaria.

3) Facultative parasite: The parasites exhibit their parasitic life when they get opportunities.

4) Obligatory parasite: Those parasites which can’t survive without a parasitic mode of life.

5) Infection: It is the method of entry and survival of the parasites into the host’s body.

6) Infectious disease: Disease caused by the infection of parasites is called infectious disease.

7) Infestation: Development and reproduction of parasites inside the host body or clothes.

· Example: Lice in clothes, Ascaris in intestine etc.

8) Immunity: Development of resistance in the host’s body against pathogens.

9) Parasitism: The association between the two species in which one (Parasite) obtains food and shelter from another species (host) with or without any harmful effects.

10) Vaccine: The liquid medicine injected into the infected person to develop resistance against the pathogens.

11) Inoculation: The method of introducing a small amount of vaccine during immunization.

12) Incubation period: It is the time period between the infection of pathogenic organisms (parasites) and the first appearance of symptoms of a disease.

13) Etiology: Science that deals with the causes of diseases.

14) Epidemiology: Study of distribution and determinants of disease in human population and its application to control health problems.

15) Prophylaxis: It is the way for prevention or control of diseases.

16) Epidemic diseases: The diseases that spread widely and rapidly among the population in one area.

17) Endemic diseases: Diseases that are confined to a particular locality, region or people

· Example: Kala-azar is endemic in Siraha and Saptari districts only.

18) Pandemic diseases: Those diseases which are epidemic over a wide geographic area that affect a large population of the area.

19) Carriers: The persons carrying pathogens.

20) Contamination: Presence of pathogens in water, milk or food used by hosts without any response to pathogens.

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