Influenza Flashcards
how many classes of influenza virus
3- A B C
which classes of influent cause human disease
A and B
which influenza is responsible for pandemic outbreaks
influenza A
what are influenza virus’
avian viruses that adapt to humans
how is influenza spread
through aerosol droplets
where does influent establish infections
establishes cytolytic infections in the epithelial of the upper and lower respiratory tract
influenza A shape
spherical or rod-shaped
structure of influenza A
spherical or rod-shaped enveloped virus covered with 2 spike like glycoproteins
name the 2 spike like glycoproteins
trimeric hemagglutinin (HA)
tetrameric neuraminidase (NA)
trimeric hemagglutinin
mediates binding to cell surfaces and internalisation
tetrameric neuraminidase
NA cleaves silica acid and promotes viral release from the cells
NA
neuraminidase
HA
hem agglutinin
DNA inside influenza
RNA
influenza infection cycle
1) HA mediates binding to cell via sialic acid
2) endocytosis of virus
3) uncoating
4) RNA replication
4) viral proteins production
5) Budding
6) viral release promoted by NA
influenza genotypes are..
diverse in birds
influenza genotypes in birds express
variety of HA and NA subtypes
types of HA expressed in birds
H1 to H15
types of NA expressed in birds
N1- N9
avian viruses prefer receptors found where
intestinal cells
what do avian virus’ bind to on intestinal cells
alpha-2,3
sialic acid linkage to galactose
what do human viruses prefer receptors found where
respiratory epithelia
what do human virus’ bind to on respiratory epithelial cells
alpha-2,6 sialic acid linkage to galactose
pigs
express both types of linkage on respiratory epithelial cells
where doe influenza virus enter human poulations
where humans, pigs and birds (waterfowl) are in close proximity
pigs can be infected with
both human and avian influenza
how do pigs mediate the production of zoonotic influenza
Pigs can be infected with both human and avian influenza, and exchange
of segments between viral genomes in the pig can give rise to variants expressing novel surface proteins together with human-adapted virulence determinants
antigenic drift
occurs due to point mutation s which accumulate in survive HA and NA - meaning that the neutralising antibodies no longer recognise the virus
point mutations in HA and NA lead to
antigenic drift
antigenic drift leads to
epidemics
when do pandemics occur
due to antigenic shift
antigenic shift
when avian influenza viruses and human influenza viruses infect pigs.
reassortment of the two genomes leads to expression of avian HA or NA in a virus otherwise adapted to infect humans
antibodies
block viral attachment to host cells
prevent release of new virions
which cells destroy infected influenza cells
CD8 T cells
human infections are usually caused by viruses that express
H1 H2 H3
N1 N2 N8 subtypes
name three influenza pandemics
spanish flu
asian flu
hong kong flu
spanish flu caused by
H1N1 (1918-1920)
asian flu caused by
H2N2 (1950s)
Hong kond fl caused by
H3N2 (1968-70)
how many deaths in the 21st century have been caused by influenza viruses
from between 2 million to 1billion
a 21st century global influenza pandemic analogous to the spanish flu is though to be
inevitable
spanish flu happened in
1918
which influenza subtype caused spanish flu
H1N1
the spanish flu’s victims were
health you adults >50% between 20 and 40 years old)
why was the spanish flu outbreak different to other flu outbreaks
due to most outbreaks killing young, elderly and weak patients
how many people died due to spnaish flu
50 mill to 100 mill
how many people killed by spanish flu in first 25 weeks
25 million
aids killed 25 million in first 25 years
why so many people killed by spanish flu
extremely high infection rates and hypokcytokinemia (thought to cause such extremes symptoms)
hypercytokinemia
cytokine strom
cytokine storm
systemic expression of a healthy and vigour immune system
what causes cytokine storm
release of over 150 inflammatory mediators
sepsis causes
systemic inflammation and coagulation
which infections cause cytokine storms
avain influenza, ARDS, sepsis and ebola
why is 21st century flu pandemic inevitable?
Highly Pathogenic Avian Influenza (HPAI) viruses, which express H5,
H7 or H9, have become established in poultry throughout China and Southeast Asia
HPAI H5N1 viruses were transmitted to individuals exposed to poultry
during outbreaks in Hong Kong in 1997
These have spread, primarily through migratory birds, to infect poultry
and humans in the Middle East and northern Africa
Human transmission of H5N1 is infrequent, but mortality approaches 60%
Pigs in China have been infected with avian H5N1 strain and the human H3N2 virus strain (responsible for the 1968-70 HK pandemic)
This may facilitate the re-assortment of viral genome segments to produce
a more transmissible virus
Influenza A pandemic (2009)
caused by a tripe re-assortment influenza A virus (H1N1) compose of human , swine and eurasian avian strain
-Efficient human-to-human transmission allows global spread of the virus
