Lecture 8: Influenza Flashcards
What are 3 types of influenza that can affect humans
Influenza C: minor hybrid which spreads between humans and pigs
Influenza B: only in humans so has been serious in the past but only one type of H and N.
Inlfluenza A: HxNx from birds that goes to infect lots of other animals (many types of H and N that can mix together)
What are the main differences between presentation of influenza and the common cold
Influenza has an abrupt systemic response whereas Cold is gradual response local to infection.
Both have sore throat but influenza has usually high fever, cough, chest problems, myalgia whereas cold has sneezing, and nasal congestion, low rates of fever.
Influenza is seasonal and severe complications due to pneumonia but cold is all year round and mild
How does influenza cause symptoms
The cells of the nose, throat and upper airways are damaged as a direct consequence of virus enveloping budding off the cells AS well AS
Build up of cytokine IFN-alpha locally which spills into the blood stream and circulates the body to cause symptoms of pain, lethargy, sense of doom and loss of appetite
Describe the cellular structure of influenza virus
RNA within protein capsid covered by an envelope made by the hosts cell membrane. Viral proteins on the cell membrane surface included haemagglutinin and neuraminidase
What is the role of haemagglutinin in the lifecycle of influenza
Haemagglutinin determines infection because it binds to sialic acid on host cells membrane, allowing it to enter the cell
How does immunity to a virus develop
After the immune system resolves the infection, antibodies are formed which bind to the specific haemagglutinin protein it encountered, blocking the virus from infecting cells.
How is immunity to influenza affected by antigenic drift
Antigenic drift: surface proteins of common viruses (antigens) change frequently due to constant mutation and this means that antibodies developed due to a prior infection no longer work on the different Haemagglutinin
What does antigenic shift mean
When a new type of influenza A virus arises
What are the 3 common influenza viruses
A: H1N1, H3N2 and B
How do neuraminidase inhibitors (eg oseltamivir) treat influenza and when should it be used
Neuraminidase inhibitors bind to neuraminidase to stop it from cleaving the haemagglutin sialic acid bond of newly budded viruses on the surface of cells, therefore stopping further spread of infection.
Best used at immediate start of illness or as prevention as side effects are bad
What is the influenza vaccination made of
Trivalent vaccine contain proteins of H1N1, H3N2 and B with a new one required most years due to antigenic drift. It mixes Haemagglutinin gene from circulating strain into a non virulent lab strain
Rate the seriousness of different types of influenzas (abc)
A: serious illness, epidemic, pandemic
B: serious illness, epidemic,
C: mild
