Although neuraminidase inhibitors are active against most 2009-2010 pandemic 
influenza A (H1N1) swine-origin strains, sporadic cases of oseltamivir 
resistance have been described. Since April 2009, 54 cases of 
oseltamivir-resistant H1N1 swine-origin have been reported in the USA 
(http://www.cdc.gov/flu/weekly/; accessed 1 February 2010). Approximately 1.4% 
of tested isolates are oseltamivir resistant. We report a patient with an 
underlying hematological malignancy who was hospitalized with influenza A (H1N1) 
swine-origin and whose strain developed oseltamivir resistance during therapy.