  We have evaluated the shear viscosity of pion gas taking into account its
scattering with the low mass resonances, $\sigma$ and $\rho$ during propagation
in the medium. The thermal width (or collisional rate) of the pions is
calculated from $\pi\sigma$ and $\pi\rho$ loop diagrams using effective
interactions in the real time formulation of finite temperature field theory. A
very small value of shear viscosity by entropy density ratio ($\eta/s$), close
to the KSS bound, is obtained which approximately matches the range of values
of $\eta/s$ used by Niemi et al. \cite{Niemi} in order to fit the RHIC data of
elliptic flow.
