Viruses Flashcards
what are the general properties of viruses
they are of a small size, and their genome can be composed of either RNA or DNA. they are metabolically inert and do not possess ribosomes. some have enzymes. not able to carry out protein synthesis on their own.
why are viruses important clinically
in relation to disease obviously but also when considering taking samples as we have to use different types of swabs and cells to grow the viruses rather than agar because they can’t grow on their own
which microbes can be grown on agar plates
bacteria and fungi
are all viruses the same size
no there are variations
what is a virion
a complete virus particles
what do virions compose of
substructures, such as lipid membranes and capsids
what are capsids
protein shell in the centre of viruses
how does herpes simplex virus appear on electron micrographs
fried egg
why are viral capsids important structures
they protect the nucleic acid genome which can be RNA or DNA
what are the stages to viral replication
- attachment
- penetration
- uncoating
- synthesis of viral components
- assembly
- release
what are the different effects that viruses can have on cells
cytopathic
transformation
latent infection
what is cytopathic infection
this is when the virus causes the cell to die
what is an example of a virus causing a cytopathic effect in its target cell
herpes simplex one and its effect on oral mucosa epithelial cells
what is transformation as an effect of viruses on cells
the cell has not been killed but has been changed to a cancerous cell
what is an example of cell transformation as a result of viral infection
papilloma virus and oral cancer
what is latent infection
this is where the virus or elements of the viral nucleic acid remain in the cell with no obvious effects on cell function
what are some viruses that cause latent infection
recurrent herpes labialis and herpes simplex
what are some diseases that viruses are responsible for
AIDS and the flu
how do viruses produce proteins
they take over the operation of cells to manufacture new viruses
what must the virus first do in order to produce proteins in the host cell
the virus must gain access and convince the machinery to make multiple copies of it
are viruses specific
yes
how is the specifity of viruses achieved
through the receptors on the membrane of the cell which the viruses use to target their specific cells for infection
why can viral DNA be described as simple
only contains the genetic information to manufacture new virus parts
what happens once the virus has entered the cell and released its DNA into the nucleus
transcribed to RNA and the protein machinery of the host will translate the instructions into new components of a virus. these parts are assembled in the host cell and emerge when ready. this usually kills the cell.
what can some viruses retain following replication within the host cell.
parts of the host cell membrane to form an envelope to protect from the immune system of the host organism.
what do anti viral drugs target
specific points in the viral life cycle to prevent it from replicating
what are the different modes of transmission for viruses
inhalation
ingestion
inoculation
congenital
sexual transmission
what is the inhalation mode of transmission
infection via the respiratory tract
what is an example of a virus that relies on inhalation
coronavirus
how does ingestion work as a mode of transmission
via the gastrointestinal tract
what is example of a virus that requires ingestion
norovirus
what is inoculation as a mode of transmission
this can be subdivided as entry via skin abrasions, mucous membranes, blood transfusions, injection, organ transplants and bites
what is an example of a virus that is transmitted via inoculation
hepatatis B transmission
what is congenital mode of transmission
from the mother to the fetus
what is an example of a virus that relies on congenital modes of transmission
rubella viral infection
what is an example of a virus that is sexually transmitted
HIV
what disease can affect the nervous system
rabies
which disease can affect the respiratory tract
adenovirus
what is an example of a localised disease of the skin and mucous membranes
herpes simplex infection
what is an example of a virus affecting the eye
adenovirus
what is an example of a virus affecting the liver
hepatitis C
what is an example of a virus affecting the salivary glands
mumps
what is an example of a virus affecting the gastrointestinal tract
norovirus
what is an example of a virus affecting the reproductive system
HIV
what is hepatitis
inflammation of the liver that can be caused by excessive alcohol consumption or through viral infection
what is hepatitis A
actute infection, transmitted through contaminated food and water, or through unprotected sex and sharing syringes
what is hepatitis C
chronic and long lasting, blood borne. children can get it from their mother if she had it while carrying. caused by sharing needles, nail clippers, tooth brushes or razors.
does hepatitis C have symptoms
no
what is hepatitis B
can be acute or chronic depending on age when transmitted. unprotected sex and sharing needles
why is it important to use viral diagnostics
diagnosis can lead to treatment
when is anti viral drug susceptibiliy important to consider
when managing conditions like HIV
which fields are coronavirus and influenza viral diagnostics important to consider
epidemiology and surveillance
what are the clinical primers for viral diagnostics
- clinical history and examination
- use a systems based approach
- surgical seive to consider what the diagnosis could be
- make a provisional diagnosis
- plan special investigations
- wide range of specimens to take
how often can virology lab manuals change
every six months
what are the different specimens to take
- swabs
- faeces
- aspirates
- plasma
- CSF
- vesicle fluids
- urine
what is an example of a virus where nucleic acid detection would be used
herpes simplex virus
what can plasma be used for
monitoring polymerase chain reaction like HIV load
what can serum be used for
serological diagnosis for hepatitis B where you are looking for antibody titres
what is the test for influenza based on
RNA - take small amounts of nucleic acid and multiply it into large amounts to enable that to quantified and more readily detected
what kind of virus is influenza
RNA
why is it important to consider influenza being an RNA virus
must be reverse transcribed before carrying out the polymerase chain reaction
how is antigen detection carried out
from blood serum, the surface antigen is detected
what can be used to distinguish the time course of a viral infection
the first class of antibody produced during acute phasing of an infection is IgM and two weeks later there is a change in class to IgG which can be used to distinguish the time course of a viral infection
