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Transcript of Viruses
an airborne disease easily spread
through sneezing or coughing of infected individuals and/or through direct contact with an infected individual's secretions from their rash
photo (cc) Malte Sörensen @ flickr
Viruses must enter a cell in order to live
Not all viruses are necessarily harmful and disease-causing
Generally, viruses are very selective when choosing their hosts
Limited number of species, tissues and cells that a virus/parasite can infect
-Both plant and animal viruses have a broad host range, capable of infecting many, many organisms
The specificity of viruses is due to:
-The specific attachment sites (receptors)
-availability of cellular factors required for viral multiplication in the host cell
Eg. animal cell membranes contain receptors for animal viruses
Interaction between the viral attachment protein
and its cellular receptor is critical
The presence or absence of these receptors determine if host is susceptible or not to viral infection
-viruses do not display many of the characteristics of living cells
- therefore viruses do not fall under the six-kingdom classification system
Viruses are classified by naming and placing the virus into a taxonomic system.
Viruses can be grouped in the
following hierarchical levels:
There are 30,000 different virus isolates known today.
There are more than 3,600
different species in 164
and 71 different families.
SO... How might we classify these
A Virus family may consist of
viruses that only develop in
plants, or bacteria.
that develop in
one of these hosts.
The basis for grouping viruses into families.
Lets compare a virus
to a person wanting to
go to a party.
There are 7 different groups
of viruses.These groups are
based on the structure of the
viral nucleic acid.
DNA, RNA, both
DNA and RNA
Single or Double stranded,
Double stranded with
regions of single strandedness
Symptoms of Chicken pox:
Early symptoms for adults and children:
loss of appetite
*followed by a rash and low-grade fever
RNA bullet shaped virus
All species of mammals are susceptible
Transmitted through the saliva of an
infected mammal to an uninfected animal
(most common through bites)
Symptoms of Rabies:
Similar to the flu, also:
Ebola is introduced into
the human population through
close contact with the blood,
secretions, organs or other
bodily fluids of infected
Ebola Virus Symptoms:
*This is followed by:
impaired kidney and liver function
*and in some cases, both internal and external bleeding.
One of the world's most
feared diseases until it was
eradicated by a collaborative
global vaccination program
led by the World Health
Small pox symptoms:
12–14 days after infection:
severe back pain
*sometimes abdominal pain & vomiting
After 2–3 days:
body temperature falls
a rash appears, first on the face, hands and forearms
it's carried in the salivary glands
is spread by direct intimate
contact such as kissing
sneezes and coughs
can also spread the virus
transmission as an airborne
pathogen is poor
virus can be transmitted
through blood transfusion
Mono virus symptoms:
swollen glands on the sides
and back of the neck,
under the arms and above the groin
fever peaking each day in late
afternoon or early evening,
sometimes up to 40.5°C (105°F)
Viral infectious (transmissible)
disease of the upper
Most common viral cause
is a rhinovirus
(a viral infective agent)
Body fluids (blood transmission- intravenous drug use, contaminated blood transfusion, medical injections with contaminated equipment)
Mother-to-child/Vertical (pregnancy, delivery, breast milk)
Stage 1: Acute infection (2-4 weeks)
- Influenza/mono-like symptoms (fever, rashes, enlarged lymph nodes, throat inflammation, sores on mouth and genitals)
- Acute retroviral syndrome or primary HIV infection
Stage 2: Clinical latency (avg. 8 years)
- beginning of stage = few/no symptoms
- end of stage = fever, weight loss, gastrointestinal problems, muscle pains
- Persistent generalized lymphadenopathy (PGL)
- towards end, viral levels increase and T-cell count drops
Stage 3: AIDS (w/o treatment- life
exp. 3 yrs.)
- T-cell count is below 200 cells/mm3
- Immune system = badly damaged
- Vulnerable to infections
The technique of replacing mutated/defective genes with DNA to prevent or treat diseases.
Tool used to deliver the functional DNA into cells, and thus slowly replace the defective DNA.
Method (through viral vectors):
Step 1: Removal of genes inside virus that would cause disease.
Step 2: Insertion of genes that code for the desired/normal effect into virus.
Step 3: Uptake of altered virus into cell.
Step 4: Normal genes attach to cell’s chromosome.
Step 5: Replication and incorporation of altered DNA.
Commonly known as the 'flu'
A respiratory (including throat, nose and lung) infection, commonly mistaken as the common cold, however there are important differences
The average person recovers within 1-2 weeks of infection, however further complications can follow such as pneumonia.
Fatigue and weakness
Long lasting fever
Severe aches and pains
- Life changing, therapeutic potential.
- Ethics/religious issues concerning altering genetic makeup (diversity loss, playing with ‘God’s work’, rich/poor divide, eugenics)
- Immune response
- Viral vectors (rediscover ability to cause disease, toxicity, stability)
- Multi-gene disorders
Development of Gene Therapy:
1972- Theodore Friedmann and Richard Rublin publish, “Gene therapy for human genetic disease?”
- 1990, 1st approved gene therapy case, temporary ADA treatment
- 1992, Dr Claudio Bordignon’s work using hematopoietic stem cells as vectors to correct hereditary diseases leads to 1st successful treatment of SCID
- New approach discovered to repair errors in RNA (potential to treat cystic fibrosis, a blood disorder, certain cancers)
- Sickle-cell disease successfully treated in mice
- 2003, method discovered (involving transfer of genes into brain) with potential to treat Parkinson’s disease
- 2006, 1st demonstration of gene therapy effect on cancer, 2 patients w/ metastatic melanoma are successfully treated
- 2007, 1st gene therapy trial for inherited retinal disease
- 2009, gene therapy used to restore monkeys’ colour vision, potential to cure human visual disorders
- 2011, gene therapy method with potential to treat Beta-Thalassemia and Sickle-Cell (clinical trial for Thalassemia expected to end- 2014
Polio is a viral disease recognized by the inflammation of nerve cells in the brain stem and spinal cord.
When an individual contracts polio, it is highly contagious.
nearly 100% of children living in the household of the contaminated person will contract it, and approximately 90% of adults.
Polio virus Symptoms:
Symptoms (nonparalytic polio):
Back pain/Neck pain or stiffness in arms and legs
Muscle spasms or tenderness
Symptoms (paralytic polio):
Loss of reflexes
Severe muscle aches and spasms
Loose and floppy limbs, often more obvious on one side of the body