Viruses Flashcards
Definition of a virus
•infective agent
•consists of nucleic acid in protein coat
•too small for light microscopy
•only lives in a host
What is the nucleocapside
•nucleic acid + capsid
What is the capsid made up of
Capsomers
6 ways viruses can be classified
1) Type of nucleic acid (RNA/DNA)
2) Number of strands (single/dbl)
3) Polarity (-ve/+ve)
4) Presence of envelope
5) Symmetry of nucleocapsid
6) Arrangement of nucleic acid (linear/circular)
What is the largest and most complex virus
Pox virus
What type of virus is coronaviridae
•RNA
•Single strand
•positive sense
•enveloped
•helical
What type of virus is orthomyxoviridae
•RNA
•single strand
•negative sense
•enveloped
•helical
What type of virus are herpesviridae and hepadnaviridae
•DNA viruses
•double stranded
•enveloped
Viral replications
•attachment + endocytosis
•uncoating + content release
•replications
•assembly stage
•release
Latent infection meaning
remains in the body in an inactive state, without causing symptoms, but can reactivate and cause illness later
Types of herpesvirus
1) Primary
2) Secondary
Secondary infection reaction
Can be 1) reactivation of latent virus
Or 2) reinfection with new virus
Describe herpes simplex 1 infections
1) Primary infection - oral ulcerations usually asymptomatic
2) enters trigeminal nerve
3) Secondary - travels down nerve and causes localised blisters
Where does Herpes Simplex 1 virus reside
Trigeminal ganglion
Varicella-zoster virus infection
1) primary - Varicella = chickenpox
2) secondary - herpes zoster = shingles
Where does Varicella-zoster virus reside
•dorsal root ganglia for decades
What family is influenza part of
Orthomyxoviruses
Proteins in the influenza envelope
•HA - hemaglutinin
•NA - neuraminidase
What does influenza A infect
•Human
•Animals - ducks, chickens, pigs, whales, horses, seals
What does influenza B infect
Humans
What type of influenza are closely related
A and B
What does influenza C infect
•not commonly humans
How is influenza A divided
•subtypes based on type of hemagglutinin and neuraminidase
How many types of hemagglutinin are there
18
•H1-18
How many types of neuraminidase are there
11
•N1-11
Current subtypes of influenza A in people
•H1N1
•H3N3
How is influenza B divided
•not into subtypes
•by lineage and strains
Current lineages of influenza B
•B/Yamagata
•B/Victoria
