From:
QUESTIONS & ANSWERS
Monitoring Influenza Activity, Including 2009 H1N1
September 11, 2009, 6:00 PM ET
http://www.cdc.gov/h1n1flu/reportingqa.htm

Question:
"If states are reporting aggregate influenza hospitalizations and deaths,
how will you tell what percentage of cases is due to 2009 H1N1 and what
percentage is due seasonal influenza viruses?"

Answer:
"Due to CDC's new case definitions, there will be no definitive way to
differentiate between hospitalizations and deaths due to seasonal influenza
versus those due to 2009 H1N1 influenza from aggregate reporting.  And some
deaths that are not due to influenza specifically will be included. However,
information on the proportion of influenza viruses that are 2009 H1N1 versus
seasonal influenza will continue to be reported in FluView from the
virologic surveillance system. (For example, as of August 29, 2009, 97% of
all subtyped influenza A viruses being reported to CDC were 2009 H1N1
viruses.)"