Viruses are microscopic particles that invade and take over host cells. They contain nucleic acid surrounded by a protein coat. Viruses reproduce by injecting their genetic material into host cells and hijacking the cell's machinery. It is debated whether viruses are living or non-living since they cannot reproduce without a host cell. Common viral diseases include colds, flu, AIDS, and many others. Vaccines help build immunity to viruses but only work against those with non-mutating proteins.

1. Viruses

2. Viruses-
• Particles of nucleic acid, protein, &
some lipids
• Any of the microscopic particles
that invade cells of plants, animals,
fungi, & bacteria.
• Often destroying the host cell.
• Parasite
• Virus= poison (Latin)
• Examples: Colds, flu, and HIV

3. Inside A Virus
• A core of genetic material
• Capsid= A protein coat
–Enables a virus to invade it’s
host.
–May be:
• DNA
• RNA

4. Living or Non-Living
• Living- • Non-Living
– Have DNA & – Crystallize
RNA – Not cells
– Heredity – Can’t make
– Reproduce proteins
– Evolve – Can’t
reproduce
w/out a host.

6. Structure Of A Virus
• Core-
–Nucleic acid
–(DNA or
RNA)
• Capsid-
–Protein coat
surrounds
core

7. Viral Reproduction
• Steps in viral
reproduction
–Recognition
–Attachment
–Injection
–Assembly
–Lysis

8. Diseases Caused by Viruses
• AIDS, Measles, Influenza
• Pathogenic viruses are
transmitted from host to host.
–Air: Chicken pox
–Water: Hepatitis
–Insects: West Nile
–See page 489

9. Fighting Viruses
• Antibiotics can’t fight viruses
• Drugs can’t destroy the virus
w/out destroying the host
• Viruses are fought with
prevention using vaccines.

10. Vaccination
• Only a healthy immune system
can fight most viral diseases.
• Vaccines build up immunity

11. Great Triumph’s
• Eliminating small
pox
• 1796 vaccine
discovered
• 1949 last case in
US
• 1977 last case of
small pox outside of

12. Filoviruses
• Viruses that live without causing
apparent harm
• Causes disease only when
infecting other animals
• Among the most dangerous
viruses

13. Filoviruses- cont
• Cause
–Hemorrhagic fever
–Attack connective tissue
–Massive bleeding
–Morality rate 30- 90%
–Ex: Ebola (1995) out break in
Zaire

14. Vaccines DO NOT Protect Against
All Viral Diseases.
• Vaccines are only effective
against viruses w/non varying
proteins on their surfaces.
• Small pox, measles, & polio
(same)
• HIV, Cold, Flu (mutate)

15. Lysogenic Infections
• Invades host & viral genetic material is
injected & then fuses w/ host’s genetic
material.
• Results in many cells being infected
with viral nucleic acid.
• This type of virus has a “dormant
period”
• HIV is a Lysogenic virus.

16. Lysogenic
Infections

17. Lytic Infections
• A virus enters a cell, makes copies of
itself, and causes the cell to lysis.
• Lysis= spreads the virus to other cells.
• The cell can no longer tell its DNA from
the virus’s DNA
• Example Bacteriophage T4

18. Back To HIV (Lysogenic Virus)
• How is it contracted
– Sex (most common)
– Blood transmissions/products
– Drug use
– Tattoos/piercings
– Birth/breastfeeding
– Healthcare settings

19. Preventing HIV (LIFE SKILL)
• Abstinence or safe sex
• Avoid drug & Alcohol use
• Use caution in healthcare settings
• Use caution when blood or other body
fluids are spilled.