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Virus
What is a Virus?
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In latin = poison
A non-cellular particle
made up of genetic material
and protein that can invade
living cells
Can only be seen by
electron microscope
Herpes Virus
Structure of a Virus
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Consists of core nucleic acid surrounded by a
protein coat (capsid)
Core is either DNA or RNA (never both)
Structure of virus
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Comes in a variety of shapes: rod, tadpole,
helical, cube-like
Vary in size from 10-400 nanometers long
(1 nanometer = 1billionth of a meter)
Bacteriophage
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A type of virus that invades bacteria and consists of
a core nucleic acid (DNA), a protein capsid (which
is the head), and a tail.
Capsid
DNA
Head
Tail
Tail Fiber
Viral Diseases
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Viruses are pathogens (disease – causing
agents) responsible for much human
suffering
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Cause human disease such as : AIDS,
smallpox, chickenpox, polio, measles,
mumps, influenza, yellow fever, rabies and
the common cold
Types of Diseases
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There are 2 main types:
1) Endemic Disease
 Disease
that are with us all the time
 Example: common cold
2) Epidemic Disease
 Diseases
that start to spread rapidly
 Example: influence and measles in the winter
Virus Transmission
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Viruses can be spread through:
1) Direct Contact
 Touching,
biting by infected animal
2) Indirect contact
 Airborne
droplets, water, food, bodily fluids
and fecal matter
Specificity of a Virus
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Usually a specific virus can only infect specific
organism (ie. Plant viruses will not affect animals;
bacteriophage will only infect bacteria)
There are millions of type of viruses, so they are
capable of infecting virtually all organisms (eg.
Bacteria, plants, insects, birds, mammals, etc.)
Girl with flu shot go
wrong