8 research outputs found

    Timeline of our study rounds and community influenza virus activity.

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    <p>In total we collected blood in seven rounds, with each of the four numbered H3N2 epidemics being neatly bracketed by two consecutive rounds of blood draws. The y-axis shows weekly influenza virus activity in Hong Kong from 2009 to 2014, measured for each influenza type/subtype as the weekly proportion of outpatient consultations associated with influenza-like-illness in sentinel outpatient clinics multiplied by the weekly proportions of laboratory specimens testing positive for influenza A(H3N2), A(H1N1)pdm09 and B viruses respectively. For each type/subtype the activity level should correlate with incidence of infections within an epidemic, but changes in consultation behaviors between epidemics (e.g. in 2009/10) may also influence observed ‘activity’ levels.</p

    Correlation between HAI titers and protection against influenza A(H3N2) virus infection.

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    <p>The upper panel shows the number of uninfected and infected persons in each pre-epidemic titer range. The lower panel shows the estimated degree of protection associated with higher pre-epidemic titers, calculated as the relative risk reduction compared with the risk at a pre-epidemic HAI titer <10.</p

    Declines in HAI titers against influenza A/Perth/16/2009(H3N2) and A/Victoria/361/2011(H3N2) virus after infection.

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    <p>In each panel the black regression lines indicate the rates of antibody waning from a fitted log-linear model, and the grey lines indicate the geometric mean titers at the center of each time point that sera were collected. There were 126 and 44 participants infected against A/Perth/16/2009(H3N2) and A/Victoria/361/2011(H3N2) respectively.</p

    Posterior distributions of parameter estimates.

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    <p>Different colors correspond to different POLYMOD contact matrices. <b>A</b> Age-dependent parameters including IARs (first column), <i>ISP</i><sub>40</sub> (second), and age-specific susceptibility (third). <b>B</b> Other parameters including <i>R</i>(0), <i>T<sub>g</sub></i>, <i>ISP</i><sub>20</sub>, reduction in within-age-group mixing due to school closure (<i>π</i><sub>0</sub>, <i>π</i><sub>1</sub>, <i>π</i><sub>2</sub>), seed size, and scaling factor for FOI from Shenzhen (<i>ε<sub>SZ</sub></i>).</p

    Prepandemic seroprevalence and the epidemic curve of pdmH1N1 in Hong Kong.

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    <p><b>A</b> Age-stratified pre-pandemic MN titer distributions which were estimated from serum samples collected in June and early-July 2009. For samples collected after July 2009, we only tested whether they were MN<sub>1∶20</sub> and MN<sub>1:40</sub> seropositive because of logistical constraints. <b>B</b> Epidemic curves of pdmH1N1 in Hong Kong and Shenzhen. Estimated weekly numbers of lab-confirmed cases in Shenzhen were extracted from <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004054#ppat.1004054-Xie1" target="_blank">[38]</a>.</p

    Age-specific Δ<i>S</i><sub>40</sub>/Δ<i>S</i><sub>20</sub> during the first wave of pdmH1N1 in Hong Kong.

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    <p>Δ<i>S</i><sub>40</sub> and Δ<i>S</i><sub>20</sub> at each cross-section were estimated using the method described in our previous work <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004054#ppat.1004054-Wu1" target="_blank">[11]</a>. If ISP<sub>20</sub> and ISP<sub>40</sub> (among all pdmH1N1 infections) were the same as the proportions of clinical cases that became MN<sub>1:20</sub> and MN<sub>1∶40</sub> seropositive (i.e. around 100% and 90%, respectively <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004054#ppat.1004054-Hung1" target="_blank">[23]</a>, <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004054#ppat.1004054-Veguilla1" target="_blank">[24]</a>), Δ<i>S</i><sub>40</sub>/Δ<i>S</i><sub>20</sub> should have remained close to 0.9–1 (the horizontal dashed line) throughout the first wave, which was not the case in reality as shown here.</p

    Comparison of the data and the fitted model.

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    <p>The hospitalization and serial cross-sectional seroprevalence data are shown in blue (vertical bars indicate 95% confidence intervals). Posterior intervals of hospitalizations and seroprevalence in the fitted model are shown as heat shades in which darker colors represent higher probability densities (i.e. highest density in red and zero density in white).</p
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