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  1. 1. Viral diseases
  2. 2. Diseases Caused by Viruses viruses are everywhere in nature, but only a few cause disease
  3. 3. Pathogens Disease Causing agents
  4. 4. Also important…Any agent (not just viruses) that causes disease is a pathogen.When a virus inserts its genetic material into a host’s DNA, it is called a provirus.Some viruses replicate very slowly and only cause damage when the conditions are “right”. (cold sores)
  5. 5. Viruses are host cell specific. Most viruses are restricted to certain kinds of cells (those that infect plants cannot infect animal cells). Why? Scientists think that viruses originated from escaped genetic material from host cells.
  6. 6. Viruses can be beneficial…Bacteriophages – attack & destroy bacteriaBaculovirus – ebola-like virus that attacks insects – Could use for pest control in crops • Cabbage loopers eat cabbage crops • Virus can kill pests in days – (it’s really gross) … and then there are those that are not so good….
  7. 7. RNA or DNA?Viruses with RNA – Human immunodeficiency virus (HIV) – Influenza viruses – RabiesViruses with DNA – Warts – Chickenpox – mononucleosis
  8. 8. Retroviruses• Contain RNA instead of DNA• Copy their RNA into DNA instead of DNA to RNA• Examples: AIDS, some cancers
  9. 9. Viral Disease in Humans • Like bacteria, viruses produce disease by disrupting the body’s normal equilibrium • Unlike bacterial diseases, viruses can’t be treated with antibiotics • The best way to protect against most viral diseases lies in prevention by the use of vaccines
  10. 10. Viral Disease in Animals • Viruses produce serious animal disease as well • Ex.) Foot-and-mouth disease, Rous sarcoma
  11. 11. Viral Disease in Plants • Many viruses infect plants • Ex.) Tobacco mosaic virus, potato yellow dwarf virus
  12. 12. Viruses are responsible for a number of plant diseases • Approximately 2,000 kinds of plant diseases have been attributed to viruses – Plant viruses are responsible for the loss of over 15 billion dollars annually by reducing the yield of important agricultural and horticultural crops • Once a plant is infected the virus spreads slowly throughout the plant • In some instances, plants have been purposefully infected with a virus in order to produce traits considered desirable by gardeners • Example: Some variegation in leaves and flowers can be brought about by viruses 16-13
  13. 13. A virus is responsible for the variegation and streaking inRembrandt tulips
  14. 14. Viroids and Prions • Scientists have discovered two virus-like particles that also cause disease
  15. 15. Viroids• Single stranded RNA molecules that have no surrounding capsid• Cause disease in plants
  16. 16. Prions• Proteins that cause disease in animalsEx.) Mad cow disease
  17. 17. Surgical masks provide protection againstthe transmission of SARS 16-21
  18. 18. Exterminating possibly infected chickens may protectagainst bird flu 16-22
  19. 19. A provirus is a DNA virus that has been inserted into ahost cell chromosome.
  20. 20. Human Immunodeficiency Virus (HIV) Acquired Immuno Deficiency Syndrome (AIDS)
  21. 21. How Is HIV Spread? • Sexual contact • Sharing contaminated needles • Blood transfusions • Breast feeding (mother to baby) • Mother to baby during pregnancy or birth
  22. 22. • HIV is a retrovirus injecting the enzyme, reverse transcriptase into the cell to copy viral RNA into DNA.
  23. 23. Viruses are host specific – a protein on the surface of thevirus has a shape that matches a molecule in the plasmamembrane of its host, allowing the virus to lock onto thehost cell.
  24. 24. • HIV doesn’t target just any cell, it goes right for the cells that want to kill it. “Helper" T cells are HIVs primary target. These cells help direct the immune systems response to various pathogens.
  25. 25. HIV undermines the bodys ability toprotect against disease by depleting Tcells thus destroying the immunesystem. After many years ofinfect 10 battle, the body has The virus can a constant billion cells ainsufficient only 1.8 billion to mount an immuneday, yet numbers of T-Cells can be replacedresponse against infections. At the point when thedaily.body is unable to fight off infections, a person is said to have the disease AIDS.It is not the virus or the disease that ultimately kills a person; it is the inability to fight off something as minor as the common cold.
  26. 26. Think about it…• In the US, there is better than a 1/1000 chance of contracting HIV during unprotected sex• A person can be contagious for more than 10 years before any sign of the disease is apparent• HIV becomes AIDS when the number of immune cells drops below a predetermined number• No one dies from HIV or AIDS; people die from secondary infections (ranging from the common cold to cancer)• More than 3 million people (size of Chicago) die each year • There are approx. 14,000 new cases of HIV worldwide every day
  27. 27. The Story of Dengue Virus
  28. 28. Dengue Virus• Single-stranded RNA virus• Causes dengue hemorrhagic fever• Transmitted by mosquitoes (Aedes aegypti)• Serotypes (DEN-1, 2, 3, 4)
  29. 29. Dengue VirusNature Structural Biology 10, 907 - 912 (2003)
  30. 30. Where?World distribution of dengue viruses and their mosquito vector, Aedes aegypti, (2005)
  31. 31. Hepatitis virus
  32. 32. Viral Hepatitis - Overview Type of Hepatitis A B C D ESource of feces blood/ blood/ blood/ fecesvirus blood-derivedblood-derived blood-derived body fluids body fluids body fluidsRoute of fecal-oral percutaneouspercutaneous percutaneous fecal-oraltransmission permucosal permucosal permucosalChronic no yes yes yes noinfectionPrevention pre/post- pre/post- blood donor pre/post- ensure safe exposure exposure screening; exposure drinking immunization immunization risk behavior immunization; water modification risk behavior modification
  33. 33. Hepatitis B virus
  34. 34. Introduction• approximately 350 million people are infected globally with HBV.
  35. 35. High-risk groups for HBV infection • People from endemic regions • Babies of mothers with chronic HBV • Intravenous drug abusers • People with multiple sex partners • Hemophiliacs and other patients requiting blood and blood product treatments • Health care personnel who have contact with blood • Residents and staff members of institutions for the mentally retarded
  36. 36. Treatment• Interferon-alpha may be effective for treating a chronic HBV infection.• Hepatitis B immune globulin may be administered within a week of exposure and to newborn infants of HBsAg-positive mothers.
  37. 37. Hepatitis C Virus
  38. 38. Introduction• The major cause of parenterally transmitted non A non B hepatitis. It eluded identification for many years. In 1989, the genome was cloned from the serum of an infected chimpanzee.
  39. 39. Transmission• Blood transfusions, blood products• organ donation• Intravenous drug abusers• community acquired: mechanism unclear. ?• Vertical transmission ?• sexual intercourse
  40. 40. Chronic Hepatitis CFactors Promoting Progression orSeverity • Increased alcohol intake • Age > 40 years at time of infection • HIV co-infection • ?Other – Male gender – Other co-infections (e.g., HBV)
  41. 41. Treatment, Prevention,and Control • Recombinant interferon-alpha is the only known effective treatment for HCV. • Illicit drug abuse and transfusion are the most identifiable sources of HCV viruses.
  42. 42. Mumps, Measles, Influenza, and Poliomyelitis
  43. 43. Chickenpox- VaricellaBlister-like rash on surface of skin and mucous membranes. Blisters usually appear first on trunk and face, then spread to almost everywhere else.
  44. 44. Kaposi’s SarcomaPurplish lesions of a skincancer not usually seen inyoung men Herpes virus
  45. 45. Rabies virus
  46. 46. Prevention and treatment