This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc., Subject name: Microbiology
Which one of the following influenza is most deadly? 
Select and explain. 
A. H1N1, B. H2N2, C. H3N2, D. H3N8
A: H1N1
Answer: A: H1N1 
Explanation: (A) H1N1 > Respiratory infection popularly known as SWINE FLU is caused by an influenza virus first recognized in spring 2009, near the end of the usual Northern Hemisphere flu season.> New virus, 2009 H1N1, spreads quickly and easily. A few months after the first cases were reported, rates of confirmed H1N1-related illness were increasing in almost all parts of the world. As a result, the World Health Organization declared the infection a global pandemic. That official designation remained in place for more than a year.