  The relative multiplicities for hadron production in different high energy
collisions are in general well described by an ideal gas of all hadronic
resonances, except that under certain conditions, strange particle rates are
systematically reduced. We show that the suppression factor gamma_s, accounting
for reduced strange particle rates in pp, pA and AA collisions at different
collision energies, becomes a universal function when expressed in terms of the
initial entropy density s_0 or the initial temperature T of the produced
thermal medium. It is found that gamma_s increases from about 0.5 to 1.0 in a
narrow temperature range around the quark-hadron transition temperature T_c =
160 MeV. Strangeness suppression thus disappears with the onset of color
deconfinement; subsequently, full equilibrium resonance gas behavior is
attained.
