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

Virus -• A nucleic acid core encased in a protein coat that

can infect cells and replicate within them

Structure of a Virus

• Capsid (protein coat)

• Nucleic Acid (DNA)

• Tail

• Tail Fibers

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.

Viral Reproduction - Lytic Cycle1. 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

1. Attachment2. Penetration3. Replication of DNA4. Protein assembly - making new viral coats5. Lysis

4

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1

Attachment/Penetration

LYSIS

MOBILITY

• Viruses do NOT move on their own

• Transferred by water, air, food, human contact

MOVEMENT

VIRAL DISEASES

Pathogenic (disease causing)

• Flu

• Hepatitis C

• Mumps

• Measles

• Ebola

• Polio

• HIVPolio

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.

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