Article from 2012 about that, and explaining why:
The previously reported number of deaths due to laboratory-confirmed H1N1 (18,500) during the 16 months of the 2009-2010 pandemic (April 2009-August 2010)1 is widely acknowledged to be a gross underestimate because most flu patients were not tested.
https://www.centerforhealthsecurity.org/cbn/2012/cbnreport_06292012.html
The previously reported number of deaths due to laboratory-confirmed H1N1 (18,500) during the 16 months of the 2009-2010 pandemic (April 2009-August 2010)1 is widely acknowledged to be a gross underestimate because most flu patients were not tested.
https://www.centerforhealthsecurity.org/cbn/2012/cbnreport_06292012.html
