  The quarks are regarded as quasiparticles, which acquire an effective mass
generated by the interaction with the other quarks of the dense system. The
bulk viscosity is re-expressed in the case of interacting strange quark matter.
We find that the viscosity is a few ~ tens times larger than that of
non-interacting quark gas due to the small correction of medium effect to the
equation of state. The limiting spins of strange stars will rise so
significantly that the pulsars with shorter period may exist.
