The first recognized case of human illness from infection with
highly pathogenic avian influenza A (H5N1) virus occurred in
May 1997 [1, 2], and 17 additional cases were detected in late
1997 in Hong Kong; overall, there were 6 deaths [3]. Two cases
were identified in February 2003 among Hong Kong family
members who traveled to southern China [4]. From November
2003 through 2 June 2009, there were 433 sporadic cases of
H5N1 virus infection reported from 15 countries [5]; in 262
(61%) of those cases, the patient died. These cases were associated
with the ongoing H5N1 panzootic among poultry and
have raised concerns of a possible H5N1 influenza pandemic,
stimulating global preparedness and response activities. Recent
reviews have summarized the development of H5N1 vaccines
and their potential use [6–8]. This article reviews the available
clinical data to date