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54 Cards in this Set
- Front
- Back
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Who is most heavily affected by influenza? |
The young and elderly are most at risk |
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How often is there an influenza pandemic? |
Every 8-40 years |
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When was the most recent flu pandemic? Caused by? |
In 2009 caused by a H1N1 strain of influenza A |
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What was the most devastating pandemic? |
Spanish influenza of 1918 - the 1918 strain |
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What are the estimates on number of deaths? |
Conservative estimates say 50 million died, some theories suggest as many as 100 million died. |
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Why is the 1918 pandemic of huge clinical significance? |
As every single pandemic strain since 1918 has it origins firmly rooted in the 1918 strain, the more the virus is like the 1918 strain, the more pathogenic it is. |
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What family do the influenza viruses belong to? |
Orthomyxoviridae |
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How many types of influenza are there? |
three, A B and C |
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Which flu strains infect humans? |
All of them |
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What is the genome of flu like? |
Segmented |
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Why is IAV most studied? |
because of its extreme pandemic potential |
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Has IBV caused a pandemic? |
No and its not expected to have the potential |
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Can IBV kill? |
Despite symptoms of IBV being milder than IAV, it can still cause severe infections and kill |
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What symptoms does ICV cause? |
mild symptoms such as dry cough |
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Does ICV have pandemic potential? |
No |
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What does ICV infect? |
the URT |
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can ICV lead to life-threatening pneumonia? |
in very rare cases. |
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What is the factor that allows IAV and IBV to bind to human cells? |
Hemagglutinin |
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What is the significant pathogenic factor of flu that can neutralise antibodies |
Hemagglutinin |
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Why doesn't ICV have pandemic potential, why is its pathogenicity lower? |
Because it lacks HA |
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How does flu spread? |
Via droplet infection |
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Why do regular epidemics and pandemics occur? |
because flu can mutate |
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What does its segmented genome allow it to do? |
Re-assort segments from its own RNA genome with segments from other influenza strains |
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What is the process of gene segment reassortment known as? |
Antigenic shift. |
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Flu is zoonotic, meaning what? |
it has animal reservoirs in which it can exist? |
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Why are animal reservoirs of importance to flu pathogenicity? Give an example |
Because cross infection and antigenic shift can occur in animals. Such as the pathogenic avian H5N1 strain. |
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What is antigenic drift? What does it cause |
Antigenic drift refers to single amino acid point mutations in the genes encoding hemagglutinin and neuraminidase. This causes a critical change in residues of the epitopes at the sites of antibody interaction, which leads to immune evasion |
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What causes seasonal epidemics? |
Antigenic drift |
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What does influenza mutation mean? |
That it is a constant threat and new vaccines must be developed regularly. |
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What is linked with influenza A virulence? |
Its replication |
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Outline the key features of flu A |
Influenza A is a negative sense RNA virus with an 8 piece segmented genome encoding for 11 proteins. |
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Describe the virions of flu A |
The virions are roughly spherical, surrounded by a lipid bilayer that holds HA and NA proteins that exist on lipid rafts. |
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What is M2? |
Matrix protein 2, a protein channel that extends though the bilayer and is important in pathogenicity |
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What does infection of flu A depend on? |
The binding of HA to sialic acid receptors of host cells |
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What do influenza strains that infect humans preferentially target? |
alpha(2-6) sugar linkages of sialic acid receptors. |
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What happens once HA has bound sialic acid receptors of host cells? |
receptor mediated endocytosis is triggered and the virus enters the cell in an endosome |
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What does HA cause the fusion of? |
Viral and host cell membranes |
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What happens after cleavage of HA by host proteases? |
HA2 fusion peptide is exposed |
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What triggers cleavage of HA? |
The acidic environment inside the endosome |
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What is the major factor in IAV virulence? |
HA |
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What does post-cleavage HA2 bind to? |
The endosomal membrane |
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What does M1 interact with? |
viral ribonucleoproteins |
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What does vRNP stand for? |
viral ribonucleoproteins |
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What does viral RNA polymerase associate with |
viral ribonucleoproteins |
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What is viral RNA polymerase complex made of? |
PB1 PB2 and PA |
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What follows the association of viral RNA polymerase with vRNPs? |
Uncoating - the low endosomal pH causes the opening of the M2 proton channel. |
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What does the opening of the M2 proton channel do? |
acidify the inside of the virion allowing the dissociation of viral RNPs from M2. |
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What does dissociation of viral RNPs from M2 allow? |
vRNP release into the cytoplasm to create viral mRNA. |
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What is M2 protein channel vital to? |
Flu replication and therefore pathogenicity. |
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How is access to HA cleavage sites granted? |
by the cleavage of neuraminic acid residues that block the receptors by NA. |
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How does NA prevent the agglutination of new virions? |
By stopping HA on one virion interacting with sialic acid residues on others. |
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How does NA free viral particles from mucosal cell linings? |
By cleaving sialic acid residues, thus freeing the virion to infect new target cells. |
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What is NA essential to? |
Viral shedding and the spread of new virions |
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What does PB1-F2 protein of influenza do? |
Lodge in the mitochondrial membranes of immune cells making the cells more sensitive to apoptosis. |
