When you say biomarker, are you looking for a signal that infection with H1N1 has started?  Like some kind of cytokine?  Prior to positive serology?  That is specific for H1N1?  I think that is a wild goose chase, meaning the likelihood that some measurable substance appears prior to positive Ab screens, and that is specific to an agent, is just not likely.  And if you are trying to take it a step further and delineate between H1N1 from all of eternity and the supposed H1N1 since 2009?  Not possible, in my view.

Kapil Patil, please, could you precise your question ?

none so far