These men start with what appears to be flu-like symptoms, and when brought to the Hospital they very rapidly develop the most vicious type of pneumonia that has ever been seen. Two hours after admission they have the mahogany spots over the cheek bones, and a few hours later you can begin to see the cyanosis extending from their ears and spreading all over the face. It is only a matter of a few hours then until death comes, and it is simply a struggle for air until they suffocate. It is horrible. (Roy as cited in Quinn, 2008, p.128–129). Source: Essential question: Why have we been able to eradicate some viruses (like polio) but not others (like HIV)?

Viruses Viruses are pathogens that 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. The influenza pandemic of killed more people than World War I, at somewhere between 20 and 40 million people. More people died of influenza in a single year than in four-years of the Black Death (1347).

Actual Size

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

Structure of DNA (review) Shape of a DOUBLE HELIX Each side held together by weak HYDROGEN BONDS Repeating units of NUCLEOTIDES Sides of "ladder" are deoxyribose and phosphates Center is A, T, G, C A -> T G -> C *base pair rule

This is a bacteriophage, a type of virus that attacks bacteria. It is recognizable because it looks like the lunar landing spaceship. See animation &feature=relatedhttp:// &feature=related Virus Structure Virus has a covering that has a capsid and sometimes an envelope Inner core contains a nucleic acid molecule (DNA or RNA) and various proteins Viruses are usually very specific to their host and to the cells they can infect.

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 & Release - viruses leave host cell to infect new cells

Viral Reproduction Lytic cycle = reproduction occurs, cells burst Lysogenic cycle = reproduction does not immediately occur (dormancy)

Types of Viruses Bacteriophages - infect bacteria Retroviruses - have RNA instead of DNA Check out this Gallery at VirusworldGallery at Virusworld

Viruses may be named according to ●the associated diseases (poliovirus, rabies) ●the type of disease caused (murine leukemia virus) ●the sites in the body affected or from which the virus was first isolated (rhinovirus, adenovirus) ●where they were first isolated (Ebola virus, Hantavirus), ●the animal that carries the virus (bird flu, swine flu) ● for the way people imagined they were contracted (dengue = ‘evil spirit’; influenza = ‘influence’ of bad air).

Focus on Human Immunodeficiency Virus (HIV)

What we know about HIV

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.

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:

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?

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

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?

Anti- Viral Drugs There are two FDA-approved antiviral drugs recommended by CDC. The brand names for these are Tamiflu® (generic name oseltamivir) and Relenza® (generic name zanamivir). Tamiflu binds to the active site on neuraminidase which prevents the virus from leaving the cell and infecting other cells Other antivirals block the viruses at various stages of their life cycle, such as blocking cell receptors, preventing attachment or preventing viral replication after the virus has entered the cell.

Various Images of Viruses for Your Viewing Pleasure

INFLUENZA

BACTERIOPHAGE

H1N1

SMALLPOX