That’s disappointingly vague. I would improve it to:
“In the spring of 2009, scientists recognized a new strain of the flu virus subtype known as H1N1.”
However, in the form you quoted it, it even more blatantly contradicts @PDPrice’s claim that “H1N1” only refers to Spanish flu, not the 2009-10 H1N1pdm09 that they circled in their graph. 