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Question
Why did the H1N1 strain of influenza virus cause a pandemic in 2009?A) The H1N1 virus had a mutation that increased the mortality associated with infection.
B) The H1N1 virus had a mutation that increased the basic reproduction number of the virus.
C) The H1N1 virus underwent a significant antigenic shift compared to other circulating strains of influenza.
D) The H1N1 virus acquired a new gene from pigs that resulted in increased virulence.
Answer
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