Question

The recent (2009) influenza pandemic was caused by which strain?

• A. H1N1
• B. H5N1
• C. H7N7
• D. H3N2

Hint:

Think swine flu, 2009, the same H and N numbers as the 1918 Spanish flu.

Answer 1

The Correct Option is A

Step 1: Recall the major influenza A subtypes and the events they caused.
Step 2: The 2009 pandemic (swine flu) was due to a novel influenza A H1N1 virus. The earlier 1918 Spanish flu pandemic was also an H1N1 virus, so H1N1 is the strain linked to the major modern pandemics.
Step 3: H5N1 is avian influenza, causing sporadic outbreaks with high mortality but not the 2009 pandemic. H7N7 and H3N2 are other influenza A subtypes; H3N2 caused the 1968 Hong Kong pandemic but not the recent one.
So the recent pandemic strain is H1N1.
Ref: Park Textbook of Preventive and Social Medicine; WHO influenza updates.