Communicable/transmissible diseases are usually caused by pathogens e.g.
bacteria, fungi, protists or viruses.
Communicable/transmissible diseases are those
in which the pathogen passes from one host to another i.e. one organism
to another, plant or animal.
(A non-communicable/non-transmissible disease
cannot be passed from one host to another.)
Health is the state of an organism's well-being
- physical or mental, but ill health is where there is a problem
including suffering from some disease.
The World Health Organisation defines heath as "a
state of complete physical, mental and social well-being, and not merely
the absence of disease or infirmity".
So, even if you are a very fit person, you are
not necessarily healthy e.g. if you had mental health issues and/or
A disease is a medical condition where part of an
organism (plant or animal) isn't functioning properly - in some way the
organism is not as it should be!
The disease may take the form of cell damage
to the host (plant or animal) which in some way impairs the healthy
('normal') structures or functions of the organism.
organisms, including ourselves, experience ill health at some point
in their life.
If you have an increased chance of contracting a
disease you are described as susceptible.
There are many causes of ill health in plants
and animals e.g.
infection from a pathogen e.g. flue,
mutation in an organism's genes (DNA)
an organism might suffer some deficiency
eg lack of vitamins in human diet, lack of light on plant growth
an organism may experience mental or
physical trauma triggered by some event eg depression,
bereavement, serious accident,
the lifestyle of an organism can have
consequences on your health eg links between: smoking and lung
cancer, too much sugary/fatty food and obesity and/or diabetes,
All diseases show symptoms at some point in
Symptoms are indications of disease in an
organism - usually observable eg cough, rash, diarrhoea, leaf
Sometimes symptoms do not show up immediately
after infection - the virus or bacteria may multiply for days or
weeks until sufficient of the pathogen is present to create visible
After a pathogen has entered an organism
(infection), there is a period of infection without symptoms
called the incubation period and may last hours, days,
weeks or months - which is a bit scary, because you can't apply
medical treatment to a medical condition you don't know you've
It is in the incubation period that
harmful toxins build up.
The more pathogen present (bacteria or
virus) the more rapidly toxins build up and you then experience
typical symptoms like headache, raised temperature, stomach
discomfort - fever etc.
Diseases can be classified as communicable and
Communicable diseases that are spread
between individual organisms - animals and people or person to person.
Because communicable diseases
can spread between organisms (plants or animals), they are often
described as contagious or infectious diseases.
They can be caused by bacteria, fungi,
parasites or viruses.
Examples are diseases like malaria,
tuberculosis or measles.
Non-communicable diseases cannot be
transmitted between individual organisms e.g. cancer, diabetes, heart
diseases (eg cardiovascular) or respiratory diseases of the lung.
See separate page on
When you have one medical condition
e.g. a communicable disease, you
may be more susceptible to another disease.
If you are suffering from one disease, your bodies
defences may be weakened by it making you more susceptible to another
disease - a 'knock on' effect reducing your body's ability to fight off
a second disease e.g.
People with problems with their immune system by which your body
defends itself against infections, may be far more susceptible to
other communicable diseases such as influenza. The body is less able
to fight off the infection from particular pathogens like the flue
Lifestyle choices and your personal situation
Eating a good balanced healthy diet helps maintain your
body in good shape and your immune system to fight communicable
disease infections and reduce the risk of contracting communicable
The poorer you diet, the weaker your
immune system is, by not accessing the correct balance of
nutrients, therefore you are more susceptible you are to
infection by pathogens.
Access to your needs?
The risk of infection from a communicable
disease increases if you have limited access to good healthcare
systems and health education.
When you have access to a quality
healthcare system, your medical condition is more likely to be
diagnosed and receive appropriate treatment. In turn this also
reduces the chance of you passing on the infection.
Education provides you with knowledge
about how diseases are transmitted and help avoid infection in
the first place - see examples down the page on HIV and safe sex
Usually no problem in rich developed countries - your choices,
BUT not so for people living in poorer underdeveloped countries.
e.g. to help prevent or reduce the risk of communicable diseases
in the first place - an you afford to buy healthy food? Is
'healthy shopping' readily available?
If you have contracted a communicable disease, do you have access
to appropriate medicines?
Do you have access to contraception e.g. condoms to prevent the
transmission of sexually transmitted disease.
Mental health and stress
If can develop a mental health condition such as depression while
enduring some physical health problem e.g. lack of mobility reducing
your ability to participate fully in everyday life.
If you are
constantly under mental stress e.g. 'high-powered' job or caring for
a very sick relative, then your physical well-being can be affected
- ulcers can develop or a mental health condition like extreme