Transcript These men start with what appears to be flu-like

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,
Source: http://www.pbs.org/wgbh/americanexperience/films/influenza/
p.128–129).
Essential question:
Why have we been able to eradicate some viruses (like polio) but
not others (like HIV)?
Viruses
The influenza pandemic of 1918-1919
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).
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.
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
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.
This is a bacteriophage, a type
of virus that attacks bacteria. It is
recognizable because it looks like
the lunar landing spaceship.
See
animation http://www.youtube.com/watch?v=41aqxcxsX2w
&feature=related
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 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.....
https://www.youtube.com/watch?v=RO8MP3wMvqg
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:
http://highered.mcgraw-hill.com/sites/007352543x/student_view0/chapter20/how_prions_arise.html
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