  Understanding the origin of infectious diseases provides scientifically based
rationales for implementing public health measures that may help to avoid or
mitigate future epidemics. The recent ancestors of a pandemic virus provide
invaluable information about the set of minimal genomic alterations that
transformed a zoonotic agent into a full human pandemic. Since the first
confirmed cases of the H1N1 pandemic virus in the spring of 2009, several
hypotheses about the strain's origins have been proposed. However, how, where,
and when it first infected humans is still far from clear. The only way to
piece together this epidemiological puzzle relies on the collective effort of
the international scientific community to increase genomic sequencing of
influenza isolates, especially ones collected in the months prior to the origin
of the pandemic.
