PMC

Phylogenetic tree illustrating genetic relation between hemagglutinin (HA) of viruses from the outbreak and from specimens obtained in other areas of the hospital and for surveillance ( n = 17). Numbers indicate maximal likelihood value. Scale bar indicates nucleotide substitutions per site. The 2009 pandemic vaccine strain (bold italic), 4 identified oseltamivir-resistant strains from this outbreak (red), strains from two other patients from the same ward before and after the outbreak (green), and 2 strains collected early in the pandemic (italic) are shown. Other strains shown are 9 strains isolated from different localities in North Carolina.

A, Gantt chart illustrating key events in illness timeline. B, spot map illustrating the location of confirmed cases of oseltamivir-resistant pandemic influenza A (H1N1) virus (pH1N1) infection within the hematology-oncology ward during the outbreak. Each patient is represented by a color. Each colored line in the Gantt chart represents the date on which a confirmed case patient (A–D) was admitted to the affected ward. Each patient's room within the hematology-oncology ward is indicated by circles with corresponding colors. Bronchoalveolar lavage (BAL) specimens collected from patient A on 15 October 2009 and 27 October 2009, as well as their grown isolates, were tested. One BAL specimen collected from patient B on 14 October 2009 and its grown isolate were also tested. Two nasal wash specimens collected from patient C on 22 October 2009 and 29 October 2009, in addition to a grown isolate, were also tested. Two nasal swab specimens collected from patient D on 14 October and 23 October 2009 and a grown virus were tested.