Viruses Flashcards
Describe why viruses can not be described as cells.
Cannot replicate independently of a host cell
What are the 3 types of virus shapes?
Icosahedral - 20 equilateral triangle faces
Helical
Complex
Most viruses have tissue tropism. What does this mean?
Specific host range
Only infect specific type of host cell
What is the name given to the extracellular form of a virus?
Virion
Describe the structure of a virion.
Nucleic acid genome and associated polymerases surrounded by protein capsid (coat)
This is surrounded by a lipid envelope (sometimes) with attachment proteins
How does a virus synthesise it’s protein coat?
It doesn’t
It steals it from the host cell that produced it
What are the 3 routes of transmission for HIV?
Blood-borne
Sexual
Vertical
What other viral infection has the same transmission routes as HIV?
Hepatitis B
Aside from HIV and Hep B, what virus is transmitted via blood?
Hepatitis C
What viruses are transmitted via the faecal-oral route?
Hepatitis A
Hepatitis E
Polio
What viruses can be caught via droplet infection?
Influenza
RSV (Respiratory syncytial virus)
What is the method of transmission of measles?
Airborne
Aside from measles, what other virus undergoes airborne transmission?
Chickenpox
Herpes simplex, CMV and EBV are transmitted through what?
Close contact
Vector borne viruses are spread by bugs. Give 3 examples of vector borne viruses, and what insect spreads them.
Dengue
Yellow fever
Chikungunya
All 3 spread by mosquitoes
Rabies, MERS and Ebola are viruses spread through what route of transmission?
Zoonotic
What is viral latency?
The virus lying dormant in the cells of the organism
Few viral antigens and no viral particles are produced
Give an example of a virus that undergoes latency.
Not HIV
Herpes simplex
Varicella zoster
Viral infection can often lead to cancer. What 3 ways can this occur?
Affects cell cycle modulation - drives cell proliferation
Prevention of apoptosis (programmed cell death)
Reactive oxygen species mediated damage
(Persistent inflammatory processes can lead to cancer via reactive oxygen species)
There are 3 basic ways to detect a virus, what are they?
Detect the whole virus
Detect part of the virus - antigens / nucleic acids
Detect an immune response to a pathogen - antibodies
One way of detecting ‘the whole virus’ is through microscopy. What is the other way?
Culture
‘All antiviral agents are virustatic, and not virucidal.’
What does this mean?
Virustatic agents prevent the growth and development of viruses, whereas virucidal agents destroy viruses.
So treatment only aims to prevent viruses from replicating, but will not kill the viruses themselves.
Some antiviral therapy is prophylactic. What does this mean?
To prevent infection = prophyaxis
Some antiviral therapy is utilised when there is evidence of infection/replication, but no symptoms are yet present. What is this called, and when is it often done?
Pre-emptive therapy
Often done after surgery and/or on immuno-suppressed patients
What is the purpose of suppressive therapy?
Keep viral replication below the level that would cause tissue damage in an asymptomatic infected patient
Summarise what types of antiviral therapy there are…
Prophylactic
Pre-emptive
Overt
Suppressive
What major viruses have been eradicated recently?
Measles
Polio
Use a single word to describe the consequence of viral infection…
Syndromes
Respiratory syndromes are caused by what?
Influenza
Measles
Chickenpox
What viruses cause neurological syndromes to develop?
Rabies Polio Enterovirus HSV VZV
Dengue fever, rubella, parvovirus and chikungunya cause arthralgia.
What is arthralgia?
Joint pain
Gastroenteritis sydromes are causes by what?
Norovirus
Rotavirus
Adenovirus
Aside from Haepatitis A, B, C, D & E, what viruses are responsible for the development of Hepatitis syndromes?
CMV
EBV
Yellow fever
Enteroviruses cause neurological syndromes and what else?
Skin infections
What does HSV cause?
Neurological syndromes
Skin infections
Eye infections
CMV, Rubella, VZV and parvovirus are responsible for causing what syndromes?
Congenital abnormalities (birth defects)
Lymphadenopathy refers to disease causing abnormalities in the size of lymph nodes. What viruses can cause this?
HIV
CMV
EBV
What viruses are responsible for causing eye infections?
HSV
VZV
Adenovirus
What are the 3 mechanisms for which a viral infection can lead to cancer
Modulation of cell cycle control
Modulation of apoptosis
Reactive oxygen species mediated damage
