Download Slide 1 - etcsciencestudents

In humans, diseases
can be caused by the
growth of
microorganisms' such
as bacteria, viruses,
and protozoa.
Finally, the damaging symptoms
of a disease can be the result of
the attempts by the host's
immune system to rid the body
of the invader. One example is
the immune-related damage
caused to the lungs of those
afflicted with cystic fibrosis
Germs must be present in the environment, either
through a person carrying the germ or through
infectious body fluids, such as discharge from the
eye, nose, mouth, or digestive (gastrointestinal)
tract; in the air; or on a surface. A person who is
not immune to the germ must come in contact with
or be exposed to the germs. The contact or
exposure must be in a way that leads to infection
Some of the symptoms you get are your own body's defences
against bacteria and viruses. Fevers, runny noses, and diarrhoea
are all ways of fighting off parasites by either making it too hot for
the parasite or trying to flush it out of the body. Unfortunately,
these are also pretty uncomfortable for you. That's why many
illnesses leave a person feeling tired or run down.
Finally, some bacteria and viruses actually release toxins into
your body that cause some of the symptoms of illness. That's
what happens when you feel nauseated and throw up after
getting food poisoning. Some of these toxins cause damage to
the body, which can lead to its own set of symptoms. So, feeling
ill is a combination of the symptoms caused by the way the
bacteria or virus attack you and the symptoms caused by your
body trying to fight off the invader