Viruses Latin for poison

I. What is a Virus? A. Viruses are particles of nucleic acid (DNA or RNA single stranded or double stranded), encased in a protein (capsid), and in some cases lipids (envelope).

B. They come in all sorts of sizes but have one thing in common only reproduce by infecting a host cell & using its parts to make more viruses. – 1. Viruses are very specific & only infect 1 type of cell and only 1 species. (host range) a. specific cell receptors (lock and key)

C. The best understood virus is the bacteriophage or phage virus, a virus that infects bacteria. – 1. there are several different types of this phage, studying this allowed scientists to understand how viruses replicate.

II. Viral Infection A. Viruses can infect a cell 2 ways: 1. Lytic Infection a.Virus enters a cell, makes copies of itself & causes the cell to burst i. Virulent phage 2. Lysogenic Infection a. Virus integrates its DNA into the host cell, & the viral genetic code (prophage) replicates along with the host cell’s DNA – i. temperate phage

III. Retroviruses A. Viruses that contain RNA as their genetic information are called retroviruses. – 1. The RNA is then copied into DNA & is joined with the host DNA (replicating backwards) with reverse transcriptase and is called a provirus. – 2. Responsible for AIDs.

IV. Are Viruses Alive?! CharacteristicVirusCell StructureDNA or RNA core, CapsidCell membrane, cytoplasm, eukaryotes contain nucleus & organelles ReproductionOnly within a host cell using the hosts transcription factors (obligate parasite) Independent cell division asexually or sexually Genetic CodeDNA or RNADNA Growth & DevelopmentyesYes; in multicellular organism Obtain/Use EnergyNoYes Response to EnvironmentyesYes Change Over TimeyesYes

V. Infectious Diseases A. Infectious diseases are ones you can catch – Example: flu, chicken pox, pneumonia B. When disease spreads… – 1. Endemic – disease that exist permanently in a particular area or population. Ex: malaria – 2. Epidemic – outbreak of disease that attacks many people at about the same time & may spread through several communities (HOT ZONE – area considered dangerous) – 3. Pandemic – epidemic spreads worldwide. Ex. HIV

V. Infectious Diseases C. Ways disease spread: – People – droplet infection, direct contact, indirect contact Patient Zero – primary case – Animals – fleas, rats, ticks, mosquitoes – Nonliving sources – food, water

VI. The C.D.C. A. The Center for Disease Control is responsible for trying to prevent deadly & dangerous diseases from coming into your home. B. The CDC works with several disease researching them to find cures, vaccines & other treatments, each disease falls under a different biosafety level 1-4; 1 being the least dangerous

VI. The C.D.C C. Levels of the C.D.C. – 1. General lab safety equipment – gloves, goggles – 2. Level 1 plus face shield – 3. Level 2 plus special mask & coat – 4. Special suit, separate air supply