Locations of changed amino acid residues of HA1 and HA2 of pH1N1 virus in Taiwan.

<p><b>A</b>. Globular head of HA1. Site Ca (Red); Site Cb Orange); Site Sa (Green); Site Sb (Blue). <b>B</b>. Stalk region of HA2. <b>C</b>. Early isolate with E374E residue. <b>D.</b> Late isolate with E374K. All the figures were generated and rendered with the use of MacPyMOL (<a href="http://wwwpymolorg" target="_blank">http://wwwpymolorg</a>). Numbers of amino acids represents the order of the amino acid taking out signal peptide (17 amino acids) and then counting the numbers from initial codon.</p

Global spatial autocorrelation analysis of E374K in Taipei metropolitan area, 2009.

<p>Global spatial autocorrelation analysis of E374K in Taipei metropolitan area, 2009.</p

Weekly distributions of positive rates of pH1N1 isolated from NTUH and YGH in Taiwan, 2009–2010.

<p>NTUH: National Taiwan University Hospital located in Taipei; YGH: Yuan's General Hospital (YGH) located in Kaohsiung. The time frames of different public health prevention/control measures was indicated with arrows.</p

Univariate analysis of the factors associated with the frequency of the pH1N1 HA E374K mutants isolated in Taiwan, 2009–2010.

<p>*: Based on the positive rate detected by RT-PCR or viral culture.</p

Odds ratios for the pH1N1-HA E374K mutants isolated in Taipei City by multivariate logistic regression analysis.

<p>Abbreviation : CI, confidence interval; OR: Odds ratio.</p><p>*p<0.05.</p

Comparison of the percentages of the pH1N1-E374K mutants in HA2 and other variants at the four antigenic sites and their relationships with different intervention strategies in various epidemic periods, 2009–2010.

1<p>. The effect of intervention of antiviral agent on the percentages of E374K mutants: Before (0%, 0/17) vs after (40.78%, 73/179), p<0.001 (Fisher's exact test).</p>2<p>. The effect of intervention of vaccination on the percentages of E374K mutants: Before (22.86%, 32/140) vs after (72.34%, 41/56), p<0.001 (Fisher's exact test).</p>3<p>. The effect of intervention of antiviral agent on the percentages of the pH1N1 variants with substitutions at four antigenic sites (Ca, Cb, Sa, Sb): Before (29.41%, 5/17) vs after (17.83%, 28/157), p = 0.324 (Fisher's exact test).</p>4<p>. The effect of intervention of vaccination on the percentages of the pH1N1 variants with substitutions at four antigenic sites (Ca, Cb, Sa, Sb): Before (11.86%, 18/118) vs after (25%, 15/56), p = 0.097 (Fisher's exact test).</p><p>*: Two strains with double mutations in Ca and Sa sites.</p><p>**: Three strains with double mutations in Ca and Sa sites.</p

Serological comparison in the antibody responses reacted with the pH1N1 isolates with various amino acid substitutions at different antigenic sites by hemagglutination inhibition (HI) tests.

1<p>ID numbers of the tested human serum samples.</p>2<p>ATCC IRR FR188 and.</p>3<p>ATCC IRR FR-187 in the 2010–2011 WHO Influenza Regent kit for diagnosis of influenza virus from the WHO Collaborating Centers for Surveillance, Epidemiology and control of Influenza at the U.S. Centers for Disease Control and Prevention.</p>4<p>HI serotiters: The highest dilution of human serum samples showed complete inhibition of 4 HA units of pH1N1 viruses.</p

Trends in increasing numbers of amino acids changes of pH1N1-HA in Taiwan, 2009–2010.

<p>Trends in increasing numbers of amino acids changes of pH1N1-HA in Taiwan, 2009–2010.</p

Comparison of the numbers of amino acid residue changes in hemagglutinin and neuraminidase of Taiwanese pH1N1 viruses between pre-peak and post-peak periods of the pH1N1 epidemic in Taipei and Kaohsiung of Taiwan, 2009–2010.

<p>*: Based on the positive rate detected by RT-PCR or virus culture.</p><p>**Compared with reference strain: A/California/07/2009.</p><p>***: Pre-peak period vs post peak period.</p><p>****:Pre-vaccination vs post-vaccination.</p