1. Viruses

2. The Facts Virus means “poison” Viruses have 3 basic parts –
Nucleic Acid
Protein coat = capsid (allows virus to enter host cell)
Lipids (sometimes)
Viruses can only reproduce by invading cells!
Two types of viruses –
Simple – involves a few genes
Complex – hundreds of genes
Viruses are highly specific.
Ex – bacteriophage are viruses that affect bacteria.

3. How do they work?
Once inside a host, virus tricks the cell into copying viral DNA/RNA instead of its own DNA.
Two types of infections:
Lytic - virus enters host cell, makes copies of itself and causes cell to burst (lyse = “burst”)
Lysogenic – virus integrates its DNA into host DNA and viral DNA replicates along with host DNA
Remains inactive for an indefinite period of time
Will become active when conditions are favorable
Prophage – viral DNA that is embedded in host DNA

4. Retroviruses Retrovirus – virus that contains RNA High mutation rate
Due to errors in replication
Leads to new viral diseases and new strains
AIDS, flu, common cold
¾ of existing diseases have originated in other animals
Hantavirus – rodents
SARS – livestock
Newest flu viruses – birds and pigs

5. Are Viruses Living??? NO!!! Why not? They need a host to reproduce
They do not grow or develop
They do not obtain or use energy
They have no response to the environment

6. How Do You Treat a Virus? You don’t!
Antibiotics are for bacterial infections, not viruses!
There are some vaccines to prevent an infection, but they don’t always work!
Ex. = flu shot – they don’t cover every strain of the flu
Other vaccines –
MMR
Hepatitis B and C
HPV

7. Examples of Viruses Cold Flu Small Pox HPV AIDS Chicken Pox Rubella
Measles
Herpes
Hepatitis
West Nile
SARS
Rabies
Mumps