After the initial atypical presentation of a patient with avian
influenza (H5N1) infection, paired acute-phase and convalescent-
phase serum samples obtained from 25 health care
workers (HCWs) who were exposed to the patient were compared
with paired serum samples obtained from 24 HCWs
who worked at different units in the same hospital and were
not exposed to the patient. There was no serologic evidence
of anti-H5 antibody reactivity or subclinical infection in either
of the groups.