Biology Today — May 2017

61

• Health is a state of optimum physical fitness, mental maturity and social well being.
• A disease is a particular abnormal, pathological condition that affects part or all of an organism. It is
often construed as a medical condition associated with specific symptoms and signs.
• In humans, “disease” is often used more broadly to refer to any condition that causes pain,
dysfunction, distress, social problems, or death to the person afflicted, or similar problems
for those in contact with the person.
• The term disease is used to refer specifically to infectious diseases that result from
the presence of pathogenic microbial agents, such as viruses, bacteria, fungi, protozoa,
multicellular organisms and aberrant proteins known as prions.
• A symptom is a sensation or change in health experienced by a patient e.g., fatigue, pain,
nausea, etc.
• Pathogen (pathos-disease, gen-causing) refers to an organism that causes certain diseases
in animals and plants, e.g., bacteria, virus, fungi, etc.
• Vectors are the carriers that do not cause disease themselves but transmit the disease causing
pathogens from infected person to a healthy person, e.g., female Anopheles mosquito is the
vector of malarial pathogen, Plasmodium.

Human Health and Diseases

Analysis of various PMTs from 2012-2016

2012

2013

2014

2015

2016

AIPMT/NEET

8

2

2

4

5

AIIMS

1

6

3

1

AMU

5

8

12

4

Kerala

1

3

K.CET

1

1

5

1

J & K

8

4

5

Class XII

Exotoxins

These are released as soon as they are

produced. The diseases brought about by

exotoxins include tetanus, diphtheria and

botulism (food poisoning).

Endotoxins

These are retained in the bacterial cells and released

when bacteria die and disintegrate. The diseases caused

by endotoxins include typhoid fever, cholera, bubonic

plague and dysentery.

Pathogens cause diseases in two ways

Toxin secretion

Many microbes produce powerful poisons,

called toxins which cause diseases.

Tissue damage

The bacteria responsible for tuberculosis, damage cells and

cause lesions in the lungs.

The bacteria that cause meningitis attack the protective

membranes, called meninges, covering the brain.

Types of toxins