Influenza

Question 1

How many types of influenza virus

Answer 1

3 - types A, B & C

Question 2

How flu vaccine works + why it has to be changed every year

Answer 2

• Body produces antibodies against the 3 flu strains in the vaccine (2 A strains and 1 B strain), after vaccination
• When exposed to flu virus, antibodies will attach onto the virus’ HA antigens, preventing flu virus from attaching to healthy cells
• Flu virus genes, made of RNA, are more prone to mutations than genes made of DNA
• If the HA gene changes, so can the antigen that it encodes, causing it to change shape
• If the HA antigen changes shape, antibodies that normally would match up to it no longer can so allowing newly mutated virus to infect healthy cells

= ANTIGENIC DRIFT