[Quick guide] The significance of 'H' and 'N' in naming a flu virus

What is the significance of 'H' and 'N' in naming a flu virus? We have all heard of viruses such as H1N1, which caused Spanish flu in 1918, Russian flu in 1977, and Swine flu in 2009. But, what do the letters 'H' and 'N', as well as the numbers, really mean in the flu's name? Now, you can understand what all of those names mean and find out why they are helpful in keeping track of the different flu viruses!

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