Influenza epidemiology Flashcards
How does the influenza virus enters a host cell
It binds sialic acid receptors via hemagglutinin and undergoes endocytosis
What triggers the fusion of the viral membrane with the host membrane
Low -ph innduced conformational changes in HA
Where does influenza virus RNA replication occur
in the nucleus of the host cell
How are new influenza virions released from the host cell
By budding at the plasma membrane
What family does the innfluenza virus belong to
Orthomyxoviridae
Which type of influenza virus has the highest pandemic potential
Influenza A
Which influenza virus primarily affects humans and causes seasonal epidemics
Influenza B
What allows influenza viruses to undergo genetic reassortment
Their segmented RNA genome
What is antigenic drift
Small mutations in HA/NA proteins causing seasonal flu variations
What is the antigenic shift
Major genetic reassortment events leading to pandemics
What does A/California/04/2009 H1/N1 represent
A= influenza type
california =first isolation location
04= isolation number
2009= year of isolation
H1N1= HA and NA subtype
What species are common hosts for influenza
Human pigs horses and birds
Why are pigs considered mixinng vessels for influenza viruses
They have both a2-3 (avian ) and a2-6 (human ) receptors allowing reassortment
What are the 2 primary transmission routes of influenza
Airborne droplets
Direct contact with contaminnated surfaces
What is the incubbation period for influenza
1-4 days
What are the common symptoms of influenza
Fever ,cough, muscle aches ,fatigue and sore throat
Who are at high risk for severe influenza complications
Elderly , immunocomprimised individuals , pregnant women
What is influenza season inn the northern hemisphere
November to March
How does climate affect innfluenza transmission
Cold temperature and low humidity enhance virus spread
Which influenza pandemic caused the highest mortality
The 1918 H1N1 pandemic (spanish flu ) caused 50 million deaths
What is a cytokine storm
An excessive immune response causing severe immunne response causinng severe inflammation seen in severe flu cases
Name 3 other influennza pandemics
1957(H2N2),1968 (H3N2) and 2009(H1N1)
Which avian influenza strains are highly pathogenic
H5N1 and H7N9
What is the significance of H5N1 in mammals
It has been detected in cattle and causes human infections
How many mutations in HA are needed for airborne transmission in ferrets
Five mutations
What global system predicts seasonal flu strains
GISRS
Name 3 types of influenza vaccines
Egg based reassortment vaccines
cDNA based vaccinnes
Universal flu vaccines
What are the main classes of antiviral drugs for influenza
M2 innhibitors (adamantanes )
Neuraminnidase innhibitors (NAIs)
RNA polymerase inhibitors
Why are adamantanes no longer reccomended
High levels of resistance
What is the mechanism of action of neuraminidase inhibitors
They block viral release from infected cells
Name an Rna polymerase inhibitor used against influenza
Baloxavir(XOfluza)
What are the 2 main mechanisms of influenza virus evolution
Antigenic drift and antigenic shift
What makes influenza pandemics possible
Genetic reassortmennt events
Why is continnuous surveilance of influenza necessary
To detect and control emerging strains before they cause pandemics
