Table of Contents
Unit 1: Introduction
- Infectious diseases affect everyone: they include everything
from the 'flu' to deadly diseases such as Ebola.
- Once thought to have been under control, infectious diseases
are back on the attack.
- New diseases with no known cure are continue to emerge. About
30 new diseases have been identified in the past 20 years.
- Old diseases that once seemed under control -- such as
diphtheria and tuberculosis -- are causing problems again. These
re-emerging diseases are developing resistance to drugs that
once cured us of their effects.
- New and re-emerging diseases are problems all over the globe
and are not limited to one region. Infectious diseases are the
leading cause of death in the world.
- The two problems of new and re-emerging diseases require that
we approach disease prevention and treatment with renewed vigour.
Unit 2: How infectious diseases work
- Diseases are caused by microbes, mainly bacteria, protozoan and
viruses. These are known as pathogens.
- Bacteria are referred to by their shapes. Bacillus are
rod-shaped; cocci are round; spirilla are spiral. Unlike viruses,
many bacteria are, in fact, essential to our well-being.
- Viruses must enter a cell in order to survive. Once inside a
cell, they multiply and kill the host cells causing the symptoms
of the infection.
- The body has three main lines of defense against pathogenic
invasion: unbroken skin and mucus membranes; white-blood cells;
antibodies, produced by B cells, and T cells.
- Vaccines work by making the body generate anti-bodies against a
specific infection and thus boost immunity.
- Anti-biotic drugs, used only for bacterial infections, are
taken after an infection has already spread. Antibiotics help
the body rid itself of the bacteria. But they also help control
the spread of diseases to non-infected people.
Unit 3: Modes of Transmission
- Viruses, bacteria and other pathogens enter our body in
numerous ways: through our respiratory system, digestive system
or breaks in our skin, for example.
- Some diseases such as influenza and tuberculosis are spread
through droplets of moisture (produced by coughing or sneezing
for instance) that we inhale.
- Some diseases such as cholera, dysentery and typhoid are spread
through unsafe water (contaminated by sewage, for instance).
- Some diseases such as malaria, dengue and yellow fever are
spread by insects (any animal that spreads infectious agents is
referred to as a vector).
- Some diseases, such as HIV/AIDS and leprosy, are transmitted
from person to person.
Unit 4: Poverty and disease
- Poverty exposes hundreds of millions of people to the hazard of
- Lack of clean water and inadequate sanitation are breeeding
grounds for infectious diseases. In developing countries, 1.1
billion people lack access to safe drinking water and some 2.9
billion people have inadequate sanitation.
- This is compounded by rapid urbanization which forces people to
live in unhygienic and overcrowded conditions.
- Poverty also leads to malnutrition which diminishes the body's
Unit 5: Prevention
- Preventive measures can be taken in a number of ways.
Vaccination is only one such method (immunization campaigns will
be discussed in the next unit).
- Keeping a healthy, well-nourished and well-hydrated body is the
first method of warding off disease.
- Keeping living eco-systems intact avoids the spread of new
diseases to humans. Some propose that a number of new diseases
have emerged because eco-systems in some regions were suddenly
disturbed by large projects such as road-building.
- Health education is another method with which the spread of
diseases and their harm can be limited. The more people know
about how diseases are spread and why, the more preventive
measures they can take.
- Among the biggest killers of infants are diarrhoeal diseases
caused by infections. The condition itself may not be deadly; it
is the secondary effect that often kills: dehydration. Oral
Rehydration Treatment (ORT) is an easy and cheap method of
- National health systems should offer protection against the
spread of diseases. In some cases, health systems have collapsed
because of the social and economic crises affecting many
Unit 6: Immunization
- Proper immunization can help keep diseases under control.
- To date, only one infectious disease -- smallpox -- has been
eradicated due to immunization efforts. Polio is targeted for
eradication by the year 2000.
- The World Health Organization spearheads many global
immunization campaigns, often with the help of other UN agencies,
such as UNICEF, governments and non-governmental organizations,
such as Rotary International.
- The Expanded Programme on Immunization, launched by WHO in
1974, has raised the immunization rate of children around the
world from 5% to 80%. It aims to raise the percentage to 90 by
the year 2000. The targets are the six vaccine-preventable
diseases that affect children most: diphteria, pertussis
(whooping cough), tetanus, poliomyelitis, measles and
- Immunization is a cheap and cost-effective method of disease
control. Immunization against the six vaccine-preventable
diseases is estimated at US$0.50 per capita in low-income
- Polio vaccines cost US$0.08. The cost of eradicating the
disease by the year 2000 is estimated by WHO at $500,000 per
year. The potential savings in terms of treatment of infected
persons are estimated at $1.5 billion per year.
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