Influenza - Zeng Flashcards
Influenza contains lipid envelope containing what 2 viral membrane proteins
Hemagglutintin ( HA)
Neuroaminidase ( NA)
What does the nucleocore contain
8-RNA segment
Nuclear matrix protein (M1)
nucleoprotein (NP)
What are the 3 types of influenza
A B C
What is influenza classification based on
- serologic cross-reactivity
- sequence similarity of M1 and NP
Which influenza type is considered harmful to humans
A and B
- C can cause disease in human but not serious human health concern
What are the subtypes in influenza type A
based on HA and NA
What are influenza type A have caused extensive outbreaks in humans
HA 1, 2, 3
NA 1, 2
H1N1
H3N2
What is antigenic drift? what types does it occur in? what does it cause?
- point mutations in HA and NA
- A and B
- epidemic infuenza
- occurs gradually
What is antigenic shift? what types does it occur in? what does it cause?
- reassortment of genomic RNA segments
- A only
- pandemic influenza
- sudden changes in HA andNA
When does flu most commonly occur? and why at this time?
winter and early spring
December to March
- low temp and low humidity
What are 2 routes of transmission for flue
airborne droplets
contaminated surfaces
how does flu interact with human cell
HA and sialic acids
what is human receptor preference
alpha 2,6 linked sailic acids
alpha 2,3 linked sailic acid
Where is alpha, 2,6 found in humans
tracheobronchial epithelium ( upper and lower tracts) type I pneumocytes
Where is alpha, 2,3 found in humans
distal bronchiole epithelium
type II pneumocytes
What is a reservoir for all A subtypes
Avian
- rarely infect humans directly
who does swine impact? what happens
humans and birds
- ‘mixing vessels’ for reassortment between avian and human viruses
How does HA influence viral infectivity
- cleavage of HA
- single basic amino acid cleavage
- extracellular cleavage only
- systemic viral replication
- multiple basic amino acid cleavage
- intracellular proteases
- viral replication
How does NA influence viral infectivity
- cleavage of sialic acids from glycoprotein
- release virions from infected cells
- prevent viral aggregation in extracellular space to enhance viral disemination
what are systemic clinical features of flu
fever malaise headache myalgia no viremia
what are respiratory clinical features of flu
dry cough
sore throat
nasal congestion/clear discharge
what is a complication of flu in children
otitis media
what are other complication of flu in children
sinusitis
primary viral pneumonia
what are secondary bacterial pneumonia
step pneumo
S . aureus
H. flu
