This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Myxo Viruses, Subject name: Microbiology
Which is the pandemic strain of influenza - 
Select and explain. 
A. H1N1, B. H2N2, C. H5N1, D. H3N3
A: H1N1
Answer: A: H1N1 
Explanation: Ans. is 'a' i.e., H1N1 Pandemic influenza A(H1N1)2009o The pandemic influenza A (HsN| ) 2009 virus differs in its pathogenicity from seasonal influenza in two key aspects.i) First, as the majority of human population has little or no pre-existing immunity to the virus, the impact of the infection has been in a wider age range, in particular among children and young adults,ii) Secondly, the virus can infect the lower respiratory tract and can cause rapidly progressive pneumonia, especially in children and young to middle-aged adults,o On 26 September 2011 WHO has adapted a newr nomenclature as influenza A (HjNi) pdm 09.