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Unformatted text preview: Biology 301 Infectious Disease & Society
Course Days: Friday Course Time: 1:30pm 4:10pm Instructor: Nathan Dougan Viruses What are viruses? "Infectious particles consisting of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope." (Campbell 1999) "is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell. Viruses infect all cellular life forms and are grouped into animal, plant and bacterial types. Over 2,000 species of virus have been discovered." (Wikipedia 2008) Viruses "any of a large group of submicroscopic infective agents that are regarded either as extremely simple microorganisms or as extremely complex molecules, that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane, that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, lower animals, or plants." (MerriamWebster 2008) Viruses "are pathogens composed of a nucleic acid genome enclosed in a protein coat. They can replicate only in a living cell, as they do not possess the metabolic machinery for independent life." (Janeway 2001) Viruses The important characteristics
1. 2. 3. Viruses are composed of nucleic acids (genetic material) that can be either DNA or RNA. These nucleic acid (genomes) are surrounded by a protein coat (capsid) Some viruses will have an membranous envelop (often host-cell phospholipid bilayer, but can have other molecules) Viruses
4. Viruses can only reproduce within a host cell (they lack the metabolic machinery to reproduce independently). 5. Viruses utilize a variety of reproductive mechanisms within host cells that may or may not kill the host. 6. Some viruses may remain "latent" in host cells until a metabolic opportunity stimulates disease-causing activity. Viruses: Structure Viruses are often categorized according to the structure of their genome. Examples
Double are: stranded DNA Single stranded DNA Double stranded RNA that can serve as mRNA Single stranded RNA that is a template for mRNA Single stranded RNA that is a template for DNA (retrovirus HIV) Viruses: Morphologies Viruses: Morphologies Viruses: Bacteriophage Viruses: Pathogenesis How do viruses cause disease? Like bacteria must adhere to and colonize a tissue, viruses must first attach to a host cell and then gain entry. Capsid or envelope proteins/glycoproteins are the keys in attachment and also in invasion. Remember that a virus must get inside the host cell in order to survive. Viruses: Pathogenesis Once inside a host cell, viruses utilize the host's metabolic machinery to make copies of the viral genome and then ship that genome out of the cell to infect more host cells. Sometimes, this process kills the host cell and sometimes the host cell may survive. Viruses: Pathogenesis Like bacteria, viruses often infect only a specific range of host cells (host range). Some viruses are very specific, while others may some variability in their targets (ex. Swine influenza, rabies). Viruses: Pathogenesis Important Lysis Concepts & Terms: / Lytic Cycle Cycle Lysogenic Virus Life Cycle Animations http://faculty.ccbcmd.edu/courses/bio141/lecgu Other http://www.hhmi.org/biointeractive/animations/ Microbiology: http://www.sumanasinc.com/webcontent/anim Vaccines http://www.pbs.org/wgbh/nova/bioterror/vacc_ Bacteria: Animations http://www.sp.uconn.edu/~terry/Common/phag Outbreak 11 (HIV/AIDS) How would you prevent this epidemic from spreading? Should the index case individual be located and informed of his status? Should the index case be threatened with legal prosecution if he persists in having unprotected sex with partners (particularly minors)? Outbreak 9 What are your thoughts on the severity of this outbreak? would propose should be done with respect to antibiotics? What Discussion Of the outbreaks you examined in this text so far, which do you feel "closest" to? In other words, which of these outbreaks is most relevant to you? Of these outbreaks, which do you believe has the most severe implications for the American public. Laws regarding infectious disease Required Immunizations ...
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- Spring '08