Influenza Flashcards
What months is influenza predominant in the northern and southern hemisphere?
northern = Dec-Feb Southern = Jun-Aug
How often do severe epidemics occur? What is this linked to?
every 11 years
sunspot activity - radiation
What is the suns influence in terms of influenza?
radiation may cause mutations leading to antigenic shifts in viral RNA
What year was Spanish flu?
1918/19
What are the 3 main groups of virus and what species do they infect?
A = mammals and birds
B and C = only humans
Describe the influenza virus
RNA virus
8 segment genome
Orthomyxoviridae family
Name the 2 surface proteins on the influenza virus
H and N
H surface protein role
Facilitates viral attachment and entry to host cell
N surface protein role
Enables new virion to be released from host cell
How many different H antigens are there and which are found in humans?
18
1-3 in humans
How many different N antigens are there?
11
Explain antigenic drift
continual point mutations over time at antibody binding sites which may change the antigenic properties and lead to vaccine mismatch and the immune system not combatting the virus as well
Explain antigenic shift
Abrupt major change in virus leading to new H/N combinations leading to pandemics as the virus can go between species
3 requirements for a pandemic
efficient person to person transmission
human pathogenicity
new virus antigenic shift in a susceptible population
Differences between seasonal and pandemic flu
seasonal happens every year in the winter months with 10-15% affected and not life threatening
pandemics occur sporadically affecting 25%+ of population and more serious
How does Avian flu spread?
direct contact with dead or alive infected birds
rarely person to person contact eg carers