  The viscous and thermal relaxation rates of an interacting fermion gas are
calculated as functions of temperature and scattering length, using a many-body
scattering matrix which incorporates medium effects due to Fermi blocking of
intermediate states. These effects are demonstrated to be large close to the
transition temperature $T_c$ to the superfluid state. For a homogeneous gas in
the unitarity limit, the relaxation rates are increased by nearly an order of
magnitude compared to their value obtained in the absence of medium effects due
to the Cooper instability at $T_c$. For trapped gases the corresponding ratio
is found to be about three due to the averaging over the inhomogeneous density
distribution. The effect of superfluidity below $T_c$ is considered to leading
order in the ratio between the energy gap and the transition temperature.
