Comparison of clinical diagnosis of children hospitalized for influenza A pH1N1 with age- matched controls hospitalized for seasonal H1N1 and H3N2, and with children hospitalized for seasonal influenza concurrently during the study period, respectively.

<p>Comparison of clinical diagnosis of children hospitalized for influenza A pH1N1 with age- matched controls hospitalized for seasonal H1N1 and H3N2, and with children hospitalized for seasonal influenza concurrently during the study period, respectively.</p

Comparisons of pre-existing high risk conditions of children hospitalized for influenza A pH1N1 with age- matched controls hospitalized for seasonal H1N1 and H3N2, and with children hospitalized for seasonal influenza concurrently during the study period, respectively.

<p>Comparisons of pre-existing high risk conditions of children hospitalized for influenza A pH1N1 with age- matched controls hospitalized for seasonal H1N1 and H3N2, and with children hospitalized for seasonal influenza concurrently during the study period, respectively.</p

Weekly numbers of specimens positive for influenza A or B, RSV, parainfluenza and adenovirus in the age groups of <1, 1–5 and 6–17 years.

<p>Weekly numbers of specimens positive for influenza A or B, RSV, parainfluenza and adenovirus in the age groups of <1, 1–5 and 6–17 years.</p

Comparison of annual excess hospitalization rates per 10,000 population and directly observed rates during each of the seven seasons, for (A) sH1N1, (B) H3N2, (C) pH1N1, (D) influenza B, (E) respiratory syncytial virus (RSV), (F) parainfluenza and (G) adenovirus.

<p>Excess hospitalization rates were derived from the WinBUGS models with age-specific counts as virus proxy.</p

Comparison of weekly directly observed rates (per 100,000 population) and excess rates of hospitalization associated with influenza estimated by the Bayesian approach, during the interpandemic period (4 January 2004–25 April 2009) and pandemic period (26 April 2009–14 August 2010).

<p>Abbreviations: RSV, respiratory syncytial virus; NA, not available.</p

Mean absolute percentage difference of excess hospitalization rates from annual hospitalization rates of laboratory confirmed infections in a pediatric cohort.

<p>Excess rates were estimated from the log-linear Poisson model using a Bayesian approach with the virus proxies of age-specific positive counts at the different lag weeks.</p

A & B. Age-specific hospitalization rates for seasonal influenza A and H1N1pdm09 (2009–2011).

<p>A & B. Age-specific hospitalization rates for seasonal influenza A and H1N1pdm09 (2009–2011).</p

Circulation of influenza A strains reflected by proportion of influenza isolates submitted to the virology laboratory of the Department of Health in Hong Kong (2003–2011).

<p>Strains with decreased homology from the previous year are denoted in bold.</p

Age-specific rates (95% CI) of hospitalization for different influenza A subtypes per 10,000 residents 2004–2011.

<p>- There was no circulation of ‘seasonal’ influenza A(H1N1) after 2010, and no circulation of influenza A(H1N1pdm09) before 2009 in Hong Kong.</p

Rate of influenza A hospitalizations per 10,000 residents <18 years: influenza A(H3N2) (gray); influenza A(H1N1) (white); influenza A(H1N1)pdm09 (black).

<p>Rate of influenza A hospitalizations per 10,000 residents <18 years: influenza A(H3N2) (gray); influenza A(H1N1) (white); influenza A(H1N1)pdm09 (black).</p