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What is a virus?
A virus is a program that self-replicates• It is not data
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RNA Bacteriophages
the maturation protein (present in the mature virus particle as asingle copy)• coat protein• lysis protein (involved in the lysis process that results in release ofmature virus particles)• a subunit of RNA replicase, the enzyme that brings aboutreplication of the viral RNA
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The single-strandedDNA genome of theThe bar represents 100 nm.Micrographs were taken with aPhilips EM 300 electronmicroscope operated at 60 kV.virus φX174 is sosmall that____are required toencode all its essential proteins. This virusprovided the first example of overlapping genes
overlapping genes
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Entrance into the cell is accompanied by theconversion of this single-stranded DNA into adouble-stranded molecule called the
replicative form (RF).
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Some single-stranded DNA viruses, such asM13, have
filamentous virions
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Single-stranded DNA Bacteriophages These viruses are very useful tools for
DNA sequencing andgenetic engineering. They are released withoutactually killing the host.
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What are vaccines?
- A vaccine is a substance that stimulates the
- body’s immune response.
- • The goal of vaccination is to prevent or control
- an infection.
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Negative-Strand RNA Viruses:
Rabies, Influenza, and Related Viruses
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Bird Flu
- Avian Influenza viruses occur naturally in wild
- birds
- • wild birds carry influenza viruses in their
- i t ti
- Bird Flu
- intestines but virus usually does not make
- wild birds sick)
- • highly contagious among birds and can make
- domesticated birds (chickens, ducks, turkey)
- sick; can be fatal
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Bird Flu in Humans
- transmission from birds to humans is possible,
- but is not sustained
- • virus obtained from direct or close contact with
- infected poultry or surfaces (secretions and/or
- excretions)
- • can also be transmitted through an intermediate
- host (ex. pig
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humans can be infected with influenza
types A, B, and C viruses
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influenza A
- is classified into subtypes according
- to surface glycoproteins hemagglutinin (HA)
- and neuraminidase (NA)
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Low and High Pathogenic Viruses
- viruses classified based on its capability of
- causing a disease
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Low Pathogenic Avian Influenza (LPAI)
- associated with mild disease in poultry; such as
- ruffled feathers and drop in egg production
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High Pathogenic Avian Influenza (HPAI)
- leads to severe illness and mortality in poultry; H5N1
- is a highly pathogenic virus
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Hepatitis A
- RNA virus;
- • transmitted enterically;
- • infect the liver;
- • clinically not distinguishable;
- • incubation period 15 to 50 days (A) and
- 22 to 60 days (E);
- • symptoms: jaundice, anorexia, vomiting,
- malaise;
- • food-associated outbreaks of hepatitis A
- recorded in great numbers: in 1988, raw
- clams were the source of nearly 300,000
- cases of hepatitis A in China;
- hepatitis A is relatively resistant to heat,
- drying, low pH, and γ-irradiation.
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Norwalk-Like Viruses
Small, round structural viruses (SRSVs), 28-38 nm in size.
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Norwalk-Like Viruses
- Symptoms: nausea, vomiting, diarrhea, and
- other symptoms common to gastroentiritis.
- Pathogenesis: the viruses infect and kill cells
- of the small intestinal mucosa
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Varicella zoster virus (VZV)
- •VZV: Chickenpox
- •VZV: Shingles
- •Re-activation of latent infection
- •Suppression of cell mediated immunity
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HIV is a Retrovirus which means
- It contains a single-stranded RNA genome
- – The HIV will incorporate it’s own genome into
- it’s host cell and hijack the normal functions of
- the cell to replicate itself
- – This process will eventually lead to cell
- destruction
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The target for HIV is
- the CD-4+ Helper TCells,
- which are the backbone of the
- immune system.
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HIV-1 GroupsGroup M (“majority
cause of the global HIV-1epidemic; many strains
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Group N (“non-O/non-M”) & Group O
(“outlier”):HIV-1 Groups
limted to Western African nations
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HIV-1 GroupsGroup M (“majority
- HIV-2 is largely restricted to West
- Africa. This suggests that HIV-2 may less efficiently
- transmitted than HIV-1
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HIV TransmissionHIV enters the bloodstream through:
- – Open Cuts
- – Breaks in the skin
- – Mucous membranes
- – Direct injection
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HIV TransmissionCommon fluids that are a means of
transmission:
- Blood
- – Semen
- – Vaginal Secretions
- – Breast Milk
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White Blood Cells
Types of WBCs
- Neutrophils
- – Eosinophils
- – Basophiles
- – Monocytes
- – Helper T cells
- – Cytotoxic T cells
- – Memory T cells
- – Suppressor T cells
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