Schematic representation of the HA molecule of the A(H1N1)pdm09 virus.

<p>HA molecules were modelled using as template the crystal structure of A 2009 H1N1 virus hemagglutinin from A/California/04/2009 (PDB 3LZG). Molecules were generated under flusurver structural model database (<a href="http://flusurver.bii.a-star.edu.sg/" target="_blank">http://flusurver.bii.a-star.edu.sg</a>). Protein sequences were blast against A/California/07/2009 to identify differences on amino acid composition. Right side HA molecule was modelled based on the strain A/Yucatan/116/2013 to indicate localization of the amino acid change S162I (red oval). The HA molecule in the middle represents the amino acidic composition of the strain A/Yucatan/81/2013 indicating the position of the mutation A141T (blue oval). Mutations at residues V234I, K283E and E499K (HA2) placed these viruses in clade 6C. Left side molecule corresponds to the HA protein sequence of the strain A/Yucatan/18/2012.</p

Temporal occurrence of genetic variants in Yucatan.

<p>Viruses from Yucatan with changes in HA and NA were distributed in time from epidemiological week 23 to 38. The bars represent the total number of influenza cases reported by the Regional Laboratory. The clear section indicates the number of confirmed cases of influenza A(H1N1)pdm09 and the grey section indicates the number of influenza A(H1N1)pdm09 viruses with genetic changes in HA and NA (HA–A141T / HA–S162I / NA–N341S / NA–L206S). The black section corresponds to the number of samples negative to influenza A(H1N1)pdm09 virus.</p

Phylogenetic tree of NA sequences of the A(H1N1)pdm09 viruses for the period 2013.

<p>Sequences from Yucatan are indicated in blue, from other regions of Mexico in red and worldwide in black. Additional amino acid changes at the node are also indicated.</p

Amino acid changes and frequency of occurrence in the hemagglutinin (HA) protein of the influenza A(H1N1)pdm09 viruses isolated in Yucatan.

<p>Frequencies of detection for each mutation are also indicated for sequences from other regions of Mexico (non-Yucatan) and worldwide for the period 2012–2013. Percentages were calculated based on the total number of sequences analysed in this study (<i>n</i>). Empty cells indicate values = 0.</p

Amino acid changes and frequency of detection in the Neuraminidase (NA) protein of the influenza A(H1N1)pdm09 virus isolated from Yucatan, Mexico (non-Yucatan) and other regions of the world for the period 2012–2013.

<p>Percentages were calculated based on the total number of sequences analysed in this study (<i>n</i>). Empty cells indicate values = 0.</p