Introduction to Viruses Flashcards
Why are viruses parasitic?
They need a host to survive
What does icosahedral mean?
It has 20 faces (in equilateral triangle)
What shape is viral DNA and RNA
helical
What does tissue tropism mean?
Most viruses have specific host range and only infect specific host cell types
What is the taxonomy of the virus?
order: mononegavirales
family: foloviridae
genus: ebolavirus
species: zaire ebolavirus
Viruses can be classified according to…(4)
- virion shape/symmetry
- presence/absence of envelope
- genome structure
- mode of replication
What nucleic acid is found inside the virus?
DNA or RNA
what structure protects DNA inside virus?
capsid
What do spike projections allow the virus to do?
develop natural immunity
What do glycoproteins on the virus surface allow it to do?
bind to receptor sites on host’s membrane (the viral envelope can the fuse with the host’s membrane to transfer viral genome)
what are steps for virus replication?
- virus attaches to cell
- genetic material enters host cell
- genetic material is uncoated
- genetic material passes into the nucleus
- more copies of genetic material are made
- cell lyses releasing more viruses
What are the 7 transmission mechanisms in humans which are involved in viral transmission?
- blood-borne
- droplet
- airborne
- vertical (mother to child)
- sexual
- close contact
- faecal-oral
What are 3 transmission mechanisms using other species to transmit viral infections?
- vector-borne(involves vectors like insects)
2. zoonotic (through animals)
what are 3 common zoonotic viruses?
- rabies
- MERS (middle east respiratory syndrome)
- ebola
what are 3 common blood borne viruses?
HIV, hep B and hep C
what are 2 common sexual viruses?
HIV, hep B (and other STIs)
what are 2 common vertical viruses?
HIV, hep B
What are 2 common droplet viruses?
influenza, RSV (respiratory, syncytial virus)
what are 3 common faecal-oral viruses?
hep A, hep E and polio
what are 2 common airborne viruses?
measles and chicken pox
what are 3 common close contact viruses?
- herpes simplex
- CMV (cytomegalovirus)
- EBV (Epstein-barr virus)
What are 3 common vector borne viruses?
- dengue
- yellow fever
- chikungunya
What is a novel virus?
- co-infection of human and animal strains in one organism may lead to recombination and generation of a new strain
- reassortment of proteins and combination of two viruses can create a new virus which can be a dangerous strain
What are the main respiratory viruses? (3)
- influenza
- measles
- chickenpox
What are the main neurological viruses? (5)
- enterovirus
- polio
- rabies
- HSV (herpes simplex)
- Varicella (VZV)
what are the main gastroenteritis viruses? (3)
- norovirus
- rotavirus
- adenovirus
what are the main hepatitis viruses? (8)
- hep ABCDE
- EBV
- CMV
- yellow fever
what are the main skin infection viruses? (2)
- herpes simplex (HSV)
- varicella (VZV)
- adenovirus
what are the main eye infections? (3)
- Herpes (HSV)
- VZV (varicella)
- adenovirus
what are the main congenital abnormalities viruses? (4)
- Cytomegalovirus (CMV)
- rubella
- varicella (VZV)
- parvovirus
what are the main lymphadenopathy viruses? (3)
- HIV
- cytomegalovirus (CMV)
- EBV (epstein barr virus)
what are the 4 main outcomes of a viral infection?
- clearance
- chronic infection
- latent infection (dormant)
- transformation
What does viral latency mean?
some viruses lie dormant in a cell, as their full viral genome is retained.
Reactivation of the virus can occur which may or may not cause the disease
which patients are at risk of having reactivation of a latent virus?
immunocompromised patients
what is an example of a latent virus?
Herpes simplex
which mechanisms cause viruses to develop into cancer? (3)
- modulation of cell cycle
- modulation of apoptosis
- reactive oxygen species mediated damage (persistent inflammatory processes)
EBV which causes mononucleosis can lead to which cancers? (4)
- Burkitt’s lymphoma
- Hodgkin’s lymphoma
- nasopharyngeal carcinoma
- post transplant lymphoproliferative disease
Human herpes virus 8 can lead to which cancers? (3)
- Kaposi’s sarcoma
- primary effusion lymphoma
- Castleman’s disease
Human T cell lymphotropic virus can lead to which cancers? (2)
- adult t cell leukaemia
- adult t cell lymphoma
HPV can lead to which cancers? (3)
- cervical
- anal
- oropharyngeal
Hepatitis B and C can lead to which cancers?
Hepatocellular carcinoma
What detection methods are used to detect the whole organism? (2)
- Electron microscopy
- virus culture
what detection method is used to detect antigen or nucleic acids?
-extraction of genetic material and amplification of region of the target organism genome (PCR used which amplified DNA)
What are the 4 reasons why antivirals might be used?
- prophylaxis (to prevent infection)
- pre-emptive therapy (evidence or replication detected but no symptoms)
- overt disease (damage to tissue or host)
- Suppressive therapy ( to keep viral replication below a certain rate in an asymptomatic patient)
what are the 5 main ways of preventing a viral infection?
- immunisation
- prophylactic treatment post exposure (e.g. rabies)
- infection prevention and control measures
- blood/tissue/organ screening
- antenatal screening (for HIV and syphillis)
What properties do viruses need to have to be officially eradicated?
- no animal reservoir or way to amplify in environment
- clearly identifiable
- no chronic carrier state (isolating/treating affected)
- efficient intervention (e.g. vaccination)
- political and social support
what are 3 examples of eradicated viruses?
- smallpox
- measles
- polio
