Biology Today — May 2017

TYPES OF DISEASES

Congenital Diseases

•    Inborn diseases, i.e., diseases with which a person is born.

Acquired Diseases

•    Diseases which are contracted after birth due to

various factors like infection, degeneration, diet, etc.

Diseases due to

environmental factors

These are caused due

to influence during the

embryonic development, e.g.,

cleft palate or harelip, etc.

Hereditary/

Genetic diseases

These are caused either due

to single gene mutation

e.g., albinism, haemophilia,

colourblindness, etc., or

chromosomal aberrations

e.g., Down’s syndrome,

Turner’s syndrome, etc.

Non-communicable/

Non-infectious diseases

These diseases remain

confined to the persons who

develop them and do not

spread in others.

Communicable/

Infectious diseases

These disease are caused by

pathogens and can spread

from infected person to a

healthy one.

Non-contagious diseases

Pathogen spreads through

a vector or vehicle, blood,

serum, food, etc.

Contagious diseases

Pathogen is transferred to

a healthy person through

contact, e.g., ringworm.

Deficiency diseases

These are produced due

to deficiency of nutrients,

minerals, vitamins

and hormones, e.g. ,

kawashiorkor, beriberi,

goitre, etc.

Mental disorders

These include emotional

instability, behavioural

dysregulation, cognitive

dysfunction or impairment,

e.g., depression, anxiety,

schizophrenia, etc.

Allergies

These are caused

when body becomes

hypersensitive to

certain foreign

substances, e.g. ,

rhinitis.

Organic diseases

These are caused

due to physical or

physiological changes

of some tissue or organ

of the body, e.g., heart

diseases, epilepsy, etc.

Cancers

These are caused by

an uncontrolled and

abnormal division of

cells which destroy

surrounding tissues,

e.g., breast cancer,

lung cancer, etc.

Addictions

These are due

to drug abuse,

alcohol or tobacco,

e.g., liver cirrhosis,

infertility, etc.

Flow chart : Classification of Diseases

Transmission of Diseases

• There are different ways through which diseases can be transmitted.

• Two main types of modes of transmission of diseases are :

(i) Direct transmission :

• The pathogens are carried directly to the human body without intermediate agents.

Various ways of direct transmission are

Direct physical contact

E.g., Chicken pox

Droplet contact

By sneezing, coughing,

spitting and talking, e.g.,

diphtheria, influenza,

measles

Contact with soil

E.g., Bacteria responsible

for tetanus

Through placenta

E.g., German measles and

syphilis

Animal bites

E.g., Rabies

(ii) Indirect transmission :

• The pathogens are carried through some intermediate agents.

Various ways of indirect transmission are

Arthropod vectors

E.g., Typhoid, cholera by

housefly

Vehicle borne

methods

E.g., AIDS, Hepatitis B

by blood

Air borne methods

E.g., Epidemic typhus

Fomite borne

methods

E.g., Influenza

Human carriers

E.g., Diphtheria, typhoid