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Influenza Virus Strains
• Type A
– moderate to severe illness – all age groups – humans and other animals
• Type B
– changes less rapidly than type A – milder epidemics – humans only – primarily affects childrennic Changes
• Antigenic Drift
– Minor change, same subtype – Caused by point mutations in gene – May result in epidemic
• Example of antigenic drift
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Influenza Vaccines
• Inactivated subunit (TIV)
– Intramuscular – Trivalent – Annual
• Live attenuated vaccine (LAIV)
– Intranasal – Trivalent – Annual
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Influenza Type A Subtypes
• Subtypes of type A determined by
hemagglutinin (H) and neuraminidase (N)
H
N
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Surface Antigens and Immunity
• Immunity reduces likelihood of
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Influenza Antigenic Changes