HA1 locations at which amino acid changes were observed in directly infected and contact pigs.

Virus derived from nasal swabs unless otherwise stated. H3 numbering [ref. 27] is used in the table and throughout the text. Where a mixed population was observed this is represented by an X with the possible mixture of amino acids described in parentheses. Dash indicates sequence data not available. Semi-quantitative nasal H1N1/09v virus shedding (REU log10).