19. Orthomyxoviruses 1 Flashcards
3 ways influenza can spread
- droplets (short distance)
- aerosols (microscopic particles in air)
- fomites on surface
most common cause of URI?
RNA viruses
what happens to vaccine efficacy when there are more serotypes in vaccine?
more serotypes in vaccine = reduced immune response
why do we have more colds in winter than summer?
kids go to school in the winter:
- kids are most common vector
- always see an increase in winter, regardless of location
is influenza the same as the common cold?
no
what happens 3 days after infection?
symptoms begin and there is max. virus shedding
what makes influenza different than other URI viruses?
other URI viruses cause endemic disease but influenza causes EPIDEMIC (in winter) and PANDEMIC disease
what type of people typically die from influenza?
old and immunocompromise
2 effects of the flu?
- infects and kills respiratory cells
- wipes out mucociliary defense
3 facts about respiratory mucociliary clearance
- uses mucus-secreting goblet cells
- uses ciliated epithelial cells
- causes a cough
describe basal cells in mucociliary system
pluripotent –> can become goblet or ciliary cells
what happens to mucociliary cells when there is infection?
increase in undifferentiated/basal cells, then eventually returns to normal cells
what type of genome does influenza have?
ssRNA segmented in 8 parts
describe the 6 proteins that make up the influenza particle
1) HA and 2) NA on the outside
3) M1 structural protein
4) 3 proteins make up polymerase
5) NP protein associated with RNA
6) NS1 nonstructural protein
describe the nucleocapsid
helical nucleocapsid of RNA + NP protein
is influenza enveloped or naked?
enveloped
what are the 3 influenza groups? how are they separated?
influenza A, B, and C
separated by nucleoprotein type
what animals can influenza A, B, and C infect?
A infects all known mammals and avian species
B and C infect humans only
does influenza A, B, or C cause pandemics?
influenza A
How many different HA gene types does influenza A have?
at least 16 completely antigenically distinct HA gene types
How many different NA gene types does influenza A have?
at least 9 completely antigenically distinct NA gene types
describe antigenic cross-reactivity between diff HA and NA types
there is NO antigenic cross-reactivity btwn diff HA and NA types
describe the antigenic drifts and shifts from H1N1
A. H1N1 (Spanish Flu) was endemic in community, then isolated to make vaccine
B. but there were gradual point mutations in HA and NA to make vaccine ineffective until H2N2 (Asian Flu) –> ANTIGENIC SHIFT #1
C. then became H3N2 (Hong Kong Flu) –> ANTIGENIC SHIFT #2
D. normally old strains were eliminated once new strain produced BUT H1N1 and H3N2 spread together
E. then H1N1 (Mexican swine flu) circulating
why is the spanish flu sometimes called swine flu?
H1N1 involved in spanish flu had HA from swine influenza
morphology of influenza particles
big floppy bags
why is there a high recombination rate in influenza viruses?
many individual RNA that can mix and match
how does recombination allow for production of attenuated vaccine virus?
use HA and NA components of antigenic virus and all other components of attenuated donor virus –> can enter cells like antigenic virus but not infect
what is the reservoir for influenza A viruses?
waterfowl
what proportion of virions are in waterfowl?
99.9%
why is bird poop liquid?
no external genitalia –> 1 channel (CLOACAE) where urine and stool mix together
describe avian influenza infection in waterfowl
multiple strains in 1 bird can multiply in cloacae without causing disease
is there a lot of genetic reassortment in avian influenza in waterfowl?
yes, high level of genetic reassortment
why are waterfowl the reservoir for avian influenza?
little/no selective pressure and genetic change –> virus just multiplies
