Figure 9: Notifications of laboratory confirmed influenza, Australia, 2004-2009,
by subtype and year of diagnosis

This figure provides a summary of the influenza subtypes circulating over the 2004 to 2009
period as a proportion. It highlights that, as a proportion, in 2009 there was a very small
amount of influenza B infections (1%) reported compared with previous years where
influenza B represented between 9 and 55% of overall notifications. Additionally, analysis of
influenza A subtyping data reported to the NNDSS for the period 2004 to 2009 highlighted a
substantial change in the reporting of subtype information. Previously an average of 8%
(range 2-14%) of influenza A notifications had subtype information, whereas in 2009 this
proportion was 68%. The substantial increase was predominately driven by the need to
identify influenza A(H1N1)pdm09 cases.