2.  Disease is any condition that may lead to
discomfort, distress, health problems, or death of
the affected person.
 There is difference between the HEALTHY and
DISEASE-FREE state of a human body.
 Diseases can be classified into acute and chronic
diseases , based on their durations.
 Diseases can also be classified into infectious and
non-infectious, based on their
 Causes for diseases can be classified into
immediate and contributory causes.

3.  Infectious diseases spread through infectious
agents(virus, bacteria, other micro-organisms).
 An infectious disease is called as a communicable
disease, if it spreads from an infected person to a
healthy person.
 Diseases caused by non infectious agent
(excessive weight, genetic defects, etc.) are called
Non-infectious disease
 Non-infectious diseases can’t be transferred from
a diseased person to a healthy person.

4.  Infectious agents(bacteria, protozoa, fungi, etc.)
 Parasites
 Contaminated food or water
 Direct physical contact
 Blood transmission
 Vectors/animals

5.  The type of causal agent determines the type of
treatment.
 But, an antibiotic meant to fight a certain
microorganism can’t fight any other
microorganism.
 For example, penicillin blocks the synthesis of the
cell wall in bacteria. This antibiotic can be used
effectively against a large number of different
bacteria. However, it cannot be used on
microorganisms such as virus.

6.  Signs and symptoms of a disease depend on the
affected tissue or organ.
 Common effects are of two types-
 local effects include swelling, pain, joint
stiffness, joint pain, etc. occurring only at the
place of infection.
 General effects include fever, chills, headache,
fatigue, loss of appetite, etc.
 All these effects are caused due to
inflammation.

7.  Reducing the effect of a disease: the side
effects/symptoms are reduced.
 Killing the cause of the disease: taking
microbe-specific medicines can kill the causal
organisms.
 It’s difficult to make anti-viral medicines, as
viruses don’t posses any cellular machinery of
their own to function.

8.  General ways:
 Cover your mouth and nose while sneezing.
 Avoid contaminated food and water.
 Ensure proper a clean environment, disposal
of sewage and a safe drinking water supply.
 Ensure availability of proper nutrition.
 Specific ways:
 This refers to defence provided by the
immune system of a person.
 Vaccination