Download viruses - Helena High School

VIRUSES AND PRIONS
STRUCTURE
•A
core nucleic acid - DNA
or RNA
•Nucleic Acid surrounded
by a protein, called a
capsid.
CLASSIFICATION
•By
genomes: DNA viruses,
RNA viruses or retroviruses
(any of a group of RNA viruses that
insert a DNA copy of their genome
into the host cell in order to
replicate, e.g., HIV.)
Evolution of Viruses
Two theories:
1)
Evolved from bits of exogenous (escaped) from
genes of larger organisms - dead bacteria?
2)
Evolved from complex molecules proteins and
nucleic acids before cells first appeared on earth
• Coevolution
between viruses and other organisms
(can be mutualistic, parasitic, or commensal)
HOSTS
• required
for viral reproduction
• All types of organisms are hosts. bacteria, fungi, humans, cows, bats,
sheep, sponges, plants, etc.
• Enter the host cell because capsid
markers adhere to receptor cells of
host
• Highjack the host DNA and reproduce
Ebola Virus
Electron micrograph of Avian Flu
Virus
Cycles of Viruses
• Lytic
Cycle – infect, reproduce, and lyse
(break-open the cell) – influenza, HPV
• Lysogenic Cycle- infect, remain dormant
(“hidden”) in the cell, a trigger will cause the
viruses to begin growing and go through the
lytic cycle (bursting) to release more viral
particles. (Shingles, HIV)
•
Amoeba Sisters Summary
•
https://s-media-cache-ak0.pinimg.com/originals/e2/0f/50/e20f508e9c5a5fcd5eb7d02f0600c823.jpg
VIRUSES
CAN BE BAD or DEADLY
- Smallpox – viral infection
- 20-60% fatality rate overall
- 80% in children
- Responsible for 300-500 million
deaths
during the early 20th century
- Eradicated in 1979 (Somalia)
Immune Response
• Antigenic
(protein) markers on capsid of the
virus cause the immune system to react.
• Immune
system produces antibodies to
attack the infection.
• Once
exposed, the immune system
remembers the antigen – re-exposure will
attack the virus before knowing you are sick
Edward Jenner and Vaccinations
• Noticed
milk maids had immunity to smallpox
• Milkmaids
were exposed to a less virulent
(dangerous) form of the virus (cowpox)
• Edward
Jenner inoculated a boy with
cowpox- the boy got sick, but recovered.
He then inoculated the boy with smallpox –
the boy did not get sick!
• Beginning
of modern day vaccinations
What is a Vaccine
•
Biological agent-improves immunity to a specific agent
•
Vacca- Latin for cow
•
Contains an agent that resembles the disease-causing
microbe
- Similar
- Killed
pathogen (cowpox for smallpox)
virus (polio)
- Weakened
- Toxin
virus (measles, mumps)
(usually bacterial- diphtheria)
1918 Flu Pandemic
I had a little bird
its name was Enza
I opened the window
And in-flu-enza
-poem 1918
Definitions
Endemic – disease regularly found in a population
• Epidemic -a widespread occurrence of an infectious disease in a
community at a particular time.
• Pandemic - whole country or the world.
• Virulence or pathogenicity– severity of a disease
(for viruses:
• a. Speed of replication,
b. ability to enter the host cell,
c. ability to evade the host immune system,
d. ability to lyse the cell)
•
epi = on, upon, above
Demic – relating to people or district
Pan=all
En= within
Definitions Continued
• Vector
-an organism that transmits a disease or
parasite
• Reservoir
(disease) – host- infectious agent
normally lives and multiplies
• Zoonotic
Infections- disease that can be transmitted
from animals to people (rabies, SARS, influenza,
Lyme disease)
1918 Flu Pandemic (Spanish flu)
• Killed
more people than the Great War or World
War I
• 38 million from WWI and approximately 50
million from 1918 flu
• 1/3 of the World Population Infected (500 million
• Normally influenza has a 0.1% fatality rate, but
1918 had increased virulence because of new
mutations- all those that may have been
immune with a slight mutation were not.
• Economic impacts and impacts to the war effort
Prions
• Caused
by a protein particle
• transmissible spongiform
encephalopathies (TSE) which
are neurodegenerative
diseases in mammals. Most
commonly known- Mad Cow
Disease, Scrapie, CJD, Kuru
• Ceph- head –
https://www.youtube.com/watch?v=ujK7KiLt0s8
Virus or Prion Project
•
Creation of a colorful, neat, presentation, poster, essay, or movie about a virus.
1.
Name of the Virus or prion – both common and scientific, if applicable, (chicken pox -
2.
Picture of the virus or prion
3.
Genome of the virus (RNA or DNA or protein if a prion)
4.
Epidemiology of the Virus or prion (reservoir(s), vectors, spreading, fatality rate, risk
factors etc.)
5.
Mention any outbreaks of the viral disease with historical implications
6.
Portion of the body infected.
7.
Symptoms of infection
8.
Preventions of infection
9.
Treatments of infection
varicella-zoster virus
20 points -