Immunology is the study of the immune system and is a very important branch of the medical and biological sciences. The immune system protects us from infection through

1. Presentation 1

2.  This module is composed of three units namely:
 Unit One: Concepts of Communicable and Non-
Communicable Diseases.
 Unit Two: Types of Communicable Diseases.
 Unit Three: Types of Non-Communicable Diseases.

3.  By the end of this module, you will be able to:
 Discuss different concepts of communicable and
non-communicable diseases
 Discuss types of communicable diseases
 Discuss types of non-communicable diseases

4.  Welcome to the first unit of this module. In this
unit you will define key terms used in
communicable and non-communicable diseases
and also differentiate between communicable and
non-communicable diseases.

5.  By the end of this unit, you will be able to:
 Define terms commonly used in communicable and
non-communicable diseases
 Classify communicable and non-communicable
diseases

6.  You will start by defining the key terms used in communicable and non-communicable
diseases. These terms include the following:
 Communicable.
 Non-communicable diseases.
 Etiology.
 Incubation.
 Manifestation.
 Control of diseases.
 Prevention of diseases.
 Primary prevention, secondary prevention and tertiary prevention.
 Emerging diseases.

7.  Re-emerging diseases.
 Vector.
 Reservoir.
 Fomite.
 Host.

8.  Communicable diseases are diseases that are
transmitted through direct contact with an infected
individual or indirectly through a vector.
 Communicable disease can also be referred as
contagious disease. Examples include the following:
 Malaria is transmitted from an infected ‘person to
another person through a vector known as a mosquito’.
 Scabies is a skin condition that is transmitted from an
infected person to another person through contact.

9.  Non-communicable diseases (NCDs) are also known as chronic
diseases. These diseases are not passed from person to person and
tend to be of long duration with slow in progression.
 Examples include the following:
 Hypertension is an example of a non-communicable disease. It is
not transmitted from one person to another. It is also a chronic
disease, that is, patients tend to have the disease for a long time.
 Cancer is another NCD which cannot be transmitted from person to
person.

10.  Etiology is a branch of medical science concerned
with the causes and origins of diseases. For
example:
 The etiology of malaria is the protozoan
plasmodium

11.  This is the development of an infection from the
time the pathogen enters the body until signs or
symptoms first appear. For example, the
incubation period for malaria is 14-21 days from
the time one is bitten by a mosquito to the onset of
signs and symptoms of malaria.

12.  This refers to a reduction in the incidence,
prevalence, morbidity or mortality of an infectious
disease to a locally acceptable level. For example,
the reduction of the number of people infected
with a disease from a high number such as 20000
infections to a tolerable level, for example 1000
infections.

13.  This is an obvious indication or specific evidence
that a disease is present. It is also known as a
symptom. For example a high fever is an early
manifestation of malaria.

14.  This refers to a reduction in the incidence,
prevalence, morbidity or mortality of an infectious
disease to a locally acceptable level. For example,
the reduction of the number of people infected
with a disease from a high number such as 20000
infections to a tolerable level, for example 1000
infections.

15.  Disease prevention covers measures not only to
prevent the occurrence of disease, such as risk
factor reduction, but also to arrest its progress and
reduce its consequences once established.

16.  Primary prevention refers to preventive measures
that stop the onset of illness or injury. This
practice focuses on the identification of potential
risk factors for disease or disability in healthy
individuals, for example, wearing seatbelts and
immunisation.

17.  These are measures aimed toward the early detection of underlying
disease when obvious clinical symptoms are not yet apparent.
The goal is to slow progression of a disease or in the case of an injury,
limiting long-term disability or preventing re-injury. Examples
include the following:
 Screening and detection of cancer, such as pap-smear and initiation
of early treatment.
 Mother attending maternal child health clinics to be screened for
syphilis, if found to be positive the clinician will initiate appropriate
treatment.

18.  Tertiary prevention is when treatment is implemented after
the disease becomes symptomatic. Focus is helping people
manage chronic health problems and preventing further
deterioration of disease or disability.
 Examples are the following:
 Surgery to treat lung cancer, rehabilitation after a stroke, and
cardiac rehabilitation post-myocardial infarction.
 Patients with diabetes mellitus should be given insulin to
maintain low blood sugar to avoid renal failure.

19.  An emerging disease is one that has appeared in a
population for the first time, or that may have
existed previously but is rapidly increasing in
incidence or geographic range (WHO, 2015).
 Examples of emerging diseases in Africa include
Ebola, avian flu, small pox and anthrax.

20.  This is any condition usually an infection that
reappears after it had been eradicated or brought
under control. For example, cholera, dengue,
diphtheria and tuberculosis

21.  A host is a person or animal that gives subsistence
to an infectious agent under natural conditions.
 For example; the host of plague is a rat and the
host of leishmaniasis is mainly canines and
rodents.

22.  Vector is an invertebrate or an animal capable of
transmitting an infectious agent to vertebrates. For
example the following:
 A flea is a vector of plague
 Mosquitos are vectors of malaria

23.  Reservoir is anything whether living or inert, in
which an infectious agent lives and multiples in
such a manner that it can be transmitted to a
susceptible host.
 Examples include the following:
 The reservoir host for trypanosomiasis is wild
herbivore
 The reservoir host for yellow fever is wild monkeys

24.  Fomites are non-living things which harbour and
transmit infectious agents to a susceptible
host. Examples are patient’s cloths and contaminated
food (Nordberg, 2005).
 By now, you should know the meaning of some of the
common terms you will be using in this course. Next
you will look at the classification of communicable and
non-communicable diseases.