Today is Tuesday, January 14 th , 2014

1. In This Lesson: Viruses (Lesson 2 of 2) Today is Tuesday,January 14th, 2014 Pre-Class: Choose one of the following: Have you ever had a virus? Which one? What does a typical computer virus do to spread itself? What does it mean when something on the web “goes viral?”

2. Today’s Agenda • Viruses! • Stuff you’ll need to know about viruses: • The three kinds we’ll talk about • Their two parts • How they “reproduce” • Where is this in my book? • Academic: P. 478 and following… • Honors: P. 200 and following…

3. Size of Viruses • Scale of the Universe

4. Virus • A virus is a non-living particle that requires a host cell to survive. • Virions are virus particles.

5. Viral Infections • Viral infections usually are not localized. • When you get the flu, it’s not just in one spot. • Examples of viruses: • Influenza • Some pneumonia • Hepatitis • Herpes • Including the Varicella-Zoster Virus – causes Chicken Pox/Shingles. • Rhinovirus • HIV • Where in the world are most viruses found? • The ocean – up to 1 billion in a single drop of water! • Estimates also suggest that same drop contains over 1 million bacteria.

6. Virus Photo Gallery • Ebola

7. Virus Photo Gallery • Herpes http://php.med.unsw.edu.au/embryology/images/d/d1/Herpes_virus.jpg

8. Virus Photo Gallery • HIV http://www.sciencedaily.com/images/2007/10/071020103343-large.jpg

9. Virus Treatment • Because viruses aren’t really alive, antibiotics don’t work on them. • Vaccines can, but they (viruses) can still evolve (just like bacteria). • This is why you hear about a different flu virus every year.

10. Parts of a Virus • Protein coat or sheath (known as a capsid) • Genetic Material (DNA OR RNA) http://www.daviddarling.info/encyclopedia/V/virus.html

11. Virus Infection/Reproduction • There are two ways viruses infect and reproduce within a host cell: • Lytic Cycle • The quick and deadly one. • Lysogenic Cycle • The slow and secretive one. • Both serve to allow the virus to copy its genetic material, just like our cells do through DNA replication.

12. Lytic Cycle

13. Lytic Cycle • During the lytic cycle, the virus injects its DNA into the host cell (or the virus is brought in entirely). • The DNA is transcribed into RNA. • The RNA is used by the ribosome to make new viruses. • Cell eventually fills with viruses and bursts (lyses), releasing copies of the virus EVERYWHERE. • Repeat.

14. Lytic Cycle vs. Lysogenic Cycle Lytic Cycle Lysogenic Cycle

15. Lysogenic Cycle • Virus injects its DNA into the host cell (or the virus is brought in entirely). • The DNA becomes part of the host cell’s original DNA. • The cell reproduces like normal and at first everything may be fine. • Later on, a mutation or other factor may “turn on” the virus part of the cell’s DNA, starting the cell into something like the lytic cycle. • In other words, they can lay dormant for a long time, even after the original infection.

17. Viral Classification • Viral classification can be really complicated. • One of the most common methods is the Baltimore system, which is based on how viruses undergo transcription:

18. Baltimore Classification • Double-stranded DNA viruses • Herpes viruses and poxviruses • Single-stranded DNA viruses • Parvovirus • Double-stranded RNA viruses • Rotavirus • Positive single-stranded RNA viruses • Rhinovirus • Negative single-stranded RNA viruses • Rabies, influenza • Single-stranded RNA viruses with reverse-transcriptase • HIV • Double-stranded DNA viruses with reverse-transcriptase • Hepatitis viruses (DNA to RNA to DNA)

19. Types of Viruses • There are three types of viruses we will discuss: • Bacteriophages • Animal Viruses (a big group) • Retroviruses (a part of animal viruses)

20. Bacteriophages • Attack bacteria. • Have a “tail” attached to the capsid that sticks to the bacterial cell.

21. Bacteriophages • Bacteriophages also seem to look suspiciously like NASA’s lunar module: http://www.theepochtimes.com/news_images/2005-5-30-phage.gif http://starchild.gsfc.nasa.gov/Images/StarChild/space_level2/apollo11_lem_big.gif

22. Which prompts a comic: http://pbfcomics.com/248/

23. Video! • T4 Bacteriophage

24. Animal Viruses • Attack eukaryotic cells – these include some of the viruses that attack us. Ebola again

25. Retroviruses(a type of Animal Virus) • These viruses use RNA (instead of DNA) andreverse transcriptase (an enzyme). • RNA is converted (reverse-transcribed) to DNA. • The DNA can then be used to infect the host. • Retroviruses often use the lysogenic cycle to reproduce. • HIV is a retrovirus. • Scary Fact: The host body produces reverse transcriptase, not the virus. • In other words, even though it does nothing for you (that we can tell at this time), your body is making the enzyme necessary for a whole group of viruses to infect you.

26. Types of Viruses

27. Influenza

28. HIV • Retrovirus that leads to AIDS. • Has RNA and reverse transcriptase. • HIV “reprograms” cells that are part of the immune system and causes them to create more HIV viruses instead of the normal immune system cells. • Mainly, HIV attacks helper T cells, the coordinators of the immune response. Remember them? • The weakened immune system leads to AIDS. http://student.biology.arizona.edu/honors2000/group15/hiv_virus_info2.html

29. HIV • Death from AIDS is caused by infection from some other pathogen because the body can’t fight back. • Note: HIV mutates so frequently (about once per replication) that over one day an infected person can produce 1,000,000,000 different copies of the virus. • Vaccines are thus difficult to develop.

30. Virus Transmission • HIV has had several high-profile means of transmission. Here are two: • Africa: AIDS Highway • Worldwide: Patient Zero

31. AIDS Highway • Technically called the Kinshasa Highway. • Stretches across the DR of Congo and Uganda. • The highway cut through sections of African rainforest that were very dense, previously isolating different populations. • After opening up travel, prostitution became prevalent and truck drivers served as a frequent vector of disease from rest stop to rest stop. http://student.biology.arizona.edu/honors2000/group15/hiv_virus_info2.html

32. Patient Zero • When HIV became widespread and AIDS came to public attention in the 1980s, the CDC tracked the outbreak to a small group of homosexual men. • Note: HIV/AIDS likely originated early in the 20th century. • One of these men was identified as a possible “center” of the network and was thus identified as Patient Zero. • GaëtanDugas, a flight attendant for Air Canada. • It remains unclear whether Dugas, who died in 1984, was actually Patient Zero, but it is clear that he continued to have unprotected sex despite knowing he had some form of contagious condition. http://s12.bdbphotos.com/images/80x80/9/h/9hs68znwu0cb08bn.jpg

33. Influenza • An outbreak of the Spanish flu led to a pandemic in 1918. Also caused by the H1N1 flu virus, it lasted two and a half years, spreading from pole to pole and across the globe, killing between 50 and 100 million people and infecting around 500 million. • That’s like killing 3+% of the human population and infecting 27+%. • More were killed than by the bubonic plague (although the population was higher). • The U.S. average life span was lowered by 10 years and over 800,000 died. • In one four-week period in Philadelphia, 12,191 people died and 47,094 cases were reported. • The pandemic seemed to end nearly as fast as it arrived. http://blog.historians.org/images/406.jpg http://4.bp.blogspot.com/-tQ08DTloWNA/TcH5ZbdjlzI/AAAAAAAAAHs/FPFkgpAZ67g/s1600/1918-flu-pandemic.jpg http://www.upenn.edu/gazette/1198/lynch4.html

34. Smallpox • Spread most often by bedsheets, clothing, and droplets of saliva, the smallpox virus had two forms. • Variola Major: Could be deadly. • Variola Minor: Less likely to be deadly. • Symptoms of both include fatigue, aches, rash, bleeding, and delirium. • During the 1970s, the WHO (World Health Organization) wiped out smallpox, leaving the only known samples in: • CDC Headquarters, Atlanta, GA • State Research Center of Virology, Koltsovo, Russia http://img.medscape.com/

35. Ebola Virus • Origin in Africa near the Ebola River, Sudan, in 1976. • Symptoms include internal and external bleeding, organ liquefaction, vomiting, chills, headache, coma, disorientation… • Outbreaks in DR Congo, Uganda, Gabon, Zaire, Sudan, have killed hundreds since then. • Spare lab accidents have killed individuals in Russia as well. • Most recent outbreak to kill more than one person was in 2009. • Near-outbreak in Reston, VA, in 1989. • Subject of The Hot Zone (and the movie Outbreak, kinda). Ebola Case #3 – Nurse Mayinga http://upload.wikimedia.org/wikipedia/commons/a/ab/7042_lores-Ebola-Zaire-CDC_Photo.jpg

36. Baculovirus • Baculovirus infects invertebrates, most notably caterpillars. • An infected caterpillar is “reprogrammed” to climb to the top of a tree where it usually dies. • The virus, having reproduced via the lytic cycle, then liquefies the caterpillar so that the next rain sends virus copies down throughout the leaves other caterpillars are eating, infecting them. http://www.trevorwilliams.info/images/ODVs_in_OB.jpg

37. Rabies • Rabies is considered the most lethal virus on the planet. • The mortality rate is effectively 100%. That’s higher than ebola. • The rabies virus (Lyssavirus) contains RNA, which ultimately interferes with RNA used by neurons/brain cells. • Late stages of the disease are characterized by mouth foaming. http://www.virology.net/big_virology/Special/Rabies1/Virions.JPG http://hlazyl.com/Rabies.html http://osp.mans.edu.eg/elsawalhy/Inf-Dis/Rabies.htm http://2.bp.blogspot.com/_F_sB-JFHT2Q/SXrE1pwPcdI/AAAAAAAAANc/maZtjmlnylw/s400/rabies.jpg

38. Let’s take a break…

39. Understanding Viruses • 4:46 • 11:16 • 28:57 • 41:53

40. Virus v. Bacteria Venn Diagram • Make yourself a large-size standard two-bubble Venn Diagram.

41. Closure and Homework • Finish the Microbiology questions! • You may work with someone on it now with the time we have left.

42. Prions • Before we close our unit on microbiology (and the semester in biology), you may be wondering where some other weird things like Mad Cow Disease fit in. • Here’s the quick story: • The big four causes of infections are bacteria, viruses, fungi, or parasites. These all have nucleic acids. • The fifth cause is prions, which are actually just misshapen protein molecules. They do not have nucleic acids.

43. Prions • Prions cause normal body proteins to also become misshapen, leading to diseases known as transmissable spongiform encephelopathies. What’s the name mean? • Transmissable because it is “contagious” in some way. • Spongiform because misshapen proteins develop pores like a sponge. • Encephelopathy because they affect the brain or nervous system. • Mad Cow Disease’s official name: Bovine Spongiform Encephelopathy (BSE). • Fun Fact: All prion-caused diseases are non-treatable and fatal.

44. Vaccines • In a moment, you’ll learn more about this, here’s a short version of how the first vaccine was researched. • In 1796, Edward Jenner injected an eight-year-old boy (James Phipps) with pus from cowpox. • He then INJECTED THE SAME KID WITH SMALLPOX! and found that he was immune. • He also injected several other children, including his own (at 11 months), and referred to the medicine as “vaccine” from vacca for cow (Latin). Edward Jenner http://www.bbc.co.uk/history/historic_figures/jenner_edward.shtml

45. Closure • Visit Quia and try the quiz called “Vaccines WebQuest.” • You’ll be searching the web for answers to these questions – the quiz will guide you.

46. Closure • Visit Quia and try the quiz called “Bioterrorism WebQuest.” • You’ll be searching the web for answers to these questions – the quiz will guide you.

47. Gapminder • For a nice close to this year’s final PowerPoint, let’s take a look at Gapminder. • This is a tool that allow us to view data on animated graphs (with four variables at a time!). • We’re going to tie this in with an activity we’ll do soon (Pandemic 2), but for now let’s just take a look at two things: HIV and sanitation.

48. Gapminder • Does income per person have any relationship to HIV spread? • www.bit.ly/OZdhSb • What trend, if any, do you see? • Does access to improved sanitation make us less likely to experience epidemics? • www.bit.ly/OZdyEF • What trend, if any, do you see?