Fig. 1.

Trends in episodes of respiratory illness and viral infection prevalence in patients seeking healthcare services within NHS Greater Glasgow and Clyde during 2005–2013. (a) Episodes of respiratory illness tested in each month highlighting the three major waves of A(H1N1)pdm09 virus circulation. (b) Distribution of episodes across age groups in each 6-month period. (c) Age-specific prevalence of confirned viral infection and virus-negative illness detected in each 6-month period. (d) Relative prevalence of each viral infection and virus-negative illness (Neg) in each 6-month period; A, typical non-influenza period (April–September); B, typical influenza period (October–March). Note that January–March 2005 and October–December 2013 were excluded from panel (d).