To analyse the appearance of amino acid substitutions at position 222 in the HA protein of circulating viruses in Spain and to determine their relationships with the disease symptoms observed.
Pandemic influenza A (H1N1) 2009 viruses detected in respiratory samples of 273 severe and 533 non-severe cases from different Spanish regions were selected for sequencing of a partial segment of HA1 subunit and studied to monitor substitutions at position 222.
D222G substitution was only detected in viruses from 14 severe cases (5.12 % ). D222E was found in viruses from 47 severe (17.21 % ) and from 52 non-severe cases (9.75 % ). D222N occurred in viruses from 3 additional severe cases (0.37 % ).
Appearance of D222G and D222E substitution in HA of pandemic influenza A (H1N1) viruses circulating in Spain might be related with severe respiratory disease.