Viruses

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Viruses

• Non-living - does not grow, eat, release waste,
  or breathe.
• Is able to reproduce, but only when inside a host
  (the cell that a virus enters)
• 100 times smaller than bacteria

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Virus -

• A nucleic acid core encased in a protein coat
  that can infect cells and replicate within them

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Structure of a Virus

• Capsid (protein coat)
• Nucleic Acid (DNA)
• Tail
• Tail Fibers

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REPRODUCTION

• 1. Viruses cannot reproduce on their own
• 2. They need a host cell to do all the work
• 3. It is a five step process called the
• Lytic Cycle that ends in the host cells death.

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Viral Reproduction - Lytic Cycle

• 1. Attachment - Virus attaches to the Host
  cell
• 2. Penetration - Virus injects its RNA or
  DNA
• 3. Replication - Host cell makes many copies
  of the viral RNA or DNA
• 4. Assembly - Host cell builds new viruses
• 5. Lysis - New viruses breaks out of host cell
  -killing it to attack other hosts

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4
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2
5
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1. Attachment 2. Penetration 3. Replication of
DNA 4. Protein assembly - making new viral
coats 5. Lysis
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Attachment/Penetration
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LYSIS
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MOBILITY

• Viruses do NOT move on their own
• Transferred by water, air, food, human contact

MOVEMENT
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VIRAL DISEASES

• Pathogenic (disease causing)
• Flu
• Hepatitis C
• Mumps
• Measles
• Ebola
• Polio
• HIV

Polio
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How are viruses treated?

• Antibiotics/medicines do NOT work on viruses
• About the only treatment is to drink plenty of
  fluids and bed rest. Some medicines may improve
  symptoms such as aspirin for fever.

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What are vaccines?

• Vaccinations (can be live, dead or weakened)
• Vaccinations prevent you from getting that
  particular virus
• The flu virus mutates so rapidly that vaccines
  are a challenge
• HIV virus attacks the immune system - mutates
  VERY rapidly - vaccine difficult