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Viruses

Adenovirus - cause of the common cold. Viruses. Viruses are insidious pathogens, they attack cells from the inside.  They hijack your own DNA and use it against you.  A virus cannot be treated with antibiotics, it can only run its course until your immune system kicks it out.

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Viruses

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  1. Adenovirus - cause of the common cold Viruses Viruses are insidious pathogens, they attack cells from the inside.  They hijack your own DNA and use it against you.  A virus cannot be treated with antibiotics, it can only run its course until your immune system kicks it out. ..Even then, the virus may lay dormant within the cells and come back at a later date

  2. Properties of viruses • no membranes, cytoplasm, ribosomes, or other cellular components • they cannot move or grow • they can only reproduce inside a host cell • they consist of 2 major parts - a protein coat, and hereditary material (DNA or RNA) • they are extremely tiny, much smaller than a cell and only visible with advanced electron microscopes

  3. Virus Structure

  4. What Is a Virus? Influenza Virus T4 Bacteriophage Tobacco Mosaic Virus RNA DNA Head RNA Capsid Tail sheath Tail fiber Membrane envelope Surface proteins Capsid proteins

  5. Parasitic Nature  Obligate intracellular parasites (they cannot exist independently) Specific to hosts (human, dog, some can cross species)  Specific to cells , the common cold is a virus that specifically attacks cells of the respiratory track (hence the coughing and sneezing and sniffling). HIV specifically attacks white blood cells This is a bacteriophage, a type of virus that attacks bacteria. It is recognizeable because it looks like the lunar landing spaceship. See animation http://www.youtube.com/watch?v=41aqxcxsX2w&feature=related

  6. Viral Reproduction Lytic cycle = reproduction occurs, cells burstLysogenic cycle = reproduction does not immediately occur (dormancy) Virulent = viruses that undergo both cycles

  7. Viruses multiply, or replicate using their own genetic material and the host cell's machinery to create more viruses. Viruses cannot reproduce on their own, and must infect a host cell in order to create more viruses. 1. Attachment 2. Penetration - the virus is engulfed by the cell                    (Cell can enter Lysogenic or Lytic Cycle) 3. Biosynthesis - viral components are made                        (protein coat, capsid, DNA/RNA) 4. Maturation - assembly of viral components 5. Release - viruses leave host cell to infect new cells                     (often destroys host)

  8. Retroviruses -- RNA viruses that have a DNA stage  • Human Immunodefiency Virus - causes AIDS  • Retrovirus (RNA inside a protein coat)  • Reverse Transcriptase makes DNA from the virus RNA  • DNA inserts into host DNA  • Proteins are assembled from the DNA code  • Viruses assembled from the proteins  • Viruses released from the cell (Link) HIV Animation - how virus infects cells

  9. Human Immunodeficiency Virus/ Acquired Immunodeficiency Syndrome By damaging your immune system, HIV interferes with your body's ability to fight off viruses, bacteria and fungi that cause disease. It is a blood born pathogen and passed from person to person and possibly animal to human. makes you more susceptible to certain types of cancers and to infections your body would normally resist, such as pneumonia and meningitis. An estimated 39.5 million people have HIV worldwide HIV/AIDS

  10. What we know about HIV.....

  11. Developing a vaccine for AIDS is difficult because it is a RETROVIRUS.  RNA mutates easily and each individual virus can be slightly different from the others.  In fact, different viruses can exist within the same person. See:  HIV coloring

  12. Emerging Viruses  illnesses not previously known  AIDS, West Nile Virus, SARS, Ebola, Bird Flu  • Could be mutations of known viruses  • Could be viruses exposed when new areas were developed  • Could have jumped species (avian flu, swine flu)

  13. Transmitted by mosquitoes One may only experience minor symptoms such as a skin rash and headache. Some develop a life-threatening illness that includes inflammation of the brain It first appeared in the United States in the summer of 1999 and since then has been found in all 48 contiguous states. How would you protect yourself? West Nile Virus

  14. SARS Virus

  15. Usually, changes in viral antigens are small. The illness these “antigenic drift” variants produce is annoying, but not usually life-threatening. But now and then a major change in antigens occurs. These “antigenic shifts” can produce devastating results -- lethal, global epidemics. The most serious occurred during World War I; It killed 675,00 Americans and between 20 and 50 million people worldwide. That’s more than all the wars of the 20th century put together.

  16. A billion people (1/2 the worlds population at the time) were infected with the flu; 40-50 million died. One year later, the pandemic was over. It was considered the deadliestpandemic in history.What caused it?... Frozen bodies in Alaska permafrost (from 1918) were autopsied and preserved lung tissue (in wax) were tested. Evidence suggests that the virus’ ancestor may have been an avian flu virus; one well-adapted to humans. What we know about the 1918 flu: The 1918 flu virus appears to have jumped, directly, from birds to humans. That jump, high virulence, and human-human transmissibility appearto be dependent on a small number ofchanges in the flu genome. Certain evolving strains of the current H5N1 avian flu strains have accumulated 5 of an estimated 10 mutations related to human-human infectivity. Swine flu of 1918 Swine flu trailer

  17. There are actually three parallel routes, any or all of which could transform the current situation into a deadly pandemic.

  18. Why are some flu strains just a nuisance, while others are dangerous? Our immune system identifies and attacks pathogens it recognizes. What if the hemogglutinin site of the virus is not known? Antibodies can’t bind!

  19. Bird migration can spread a bird virus around the world! People travel, too.

  20. What’s the problem? • Swine flu is really a bird flu that’s changed…and keeps changing. • The virus can evolve in other animals, so your body can’t recognize it. It can make you very sick or kill you…jut like regular human Influenza A. • How do you protect yourself? • Wash your hands often. • Stay away from sick people. • Keep your immune system strong by eating healthy, sleeping enough, and exercising. • Get a flu shot if you are in a high risk group. • Stay away from well people, when you are sick. Get medical attention. H1N1 Swine Flu

  21. How Do Vaccines Work? 1.  Once you have gotten a virus, such as chicken pox, your body develops the immunity to that virus.   2. Vaccines are made by growing a weakened or killed form of the virus (often grown in eggs) 3.  This form of the virus is injected into a person's body, which causes an immune response, and immunity to the virus.    - Remember Jenner's cowpox vaccine?

  22. RV = rotovirus; DTaP = diptheria, tetanus, pertussis (whooping cough);  Hib = haemophilus influenza type B;  PCV = pneumococcal vaccine; IPV = inactivated polio virus;  MMR = measles, mumps, rubella,  

  23. Some parents are opting out of immunizations due to fears about vaccine safety.   In response, government agencies are producing commercials to encourage parents to get their child vaccinated. Discuss: 1.  What are the risks of vaccines?  Are they safe? 2.  Would you have your own child vaccinated?3.  Should the government force immunizations?

  24. INFLUENZA

  25. BACTERIOPHAGE

  26. H1N1

  27. SMALLPOX

  28. How big are viruses?

  29. Related to Viruses Viroids - even smaller than viruses, consist of RNA strands that lack a protein coat Prions - "rogue protein", believed to be the cause of Mad Cow Disease, also may cause Kuru in cannibal tribes See:  http://highered.mcgraw-hill.com/sites/007352543x/student_view0/chapter20/how_prions_arise.html

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