Viruses

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.

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

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

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

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

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