  We determine the shear viscosity of a hot and dense Yukawa-Fermi gas, using
the standard Green-Kubo relation, according to which the shear viscosity is
given by the retarded correlator of the traceless part of viscous
energy-momentum tensor. We approximate this retarded correlator using a
one-loop skeleton expansion, and express the bosonic and fermionic shear
viscosities, $\eta_{b}$ and $\eta_{f}$, in terms of bosonic and fermionic
spectral widths, $\Gamma_{b}$ and $\Gamma_{\pm}$. Here, the subscripts $\pm$
correspond to normal and collective (plasmino) excitations of fermions. We
study, in particular, the effect of these excitations on thermal properties of
$\eta_{f}[\Gamma_{\pm}]$. To do this, we determine first the dependence of
$\Gamma_{b}$ and $\Gamma_{\pm}$ on momentum $p$, temperature $T$, chemical
potential $\mu$ and $\xi_{0}\equiv m_{b}^{0}/m_{f}^{0}$, in a one-loop
perturbative expansion in the orders of the Yukawa coupling. Here, $m_{b}^{0}$
and $m_{f}^{0}$ are $T$ and $\mu$ independent bosonic and fermionic masses,
respectively. We then numerically determine $\eta_{b}[\Gamma_{b}]$ and
$\eta_{f}[\Gamma_{\pm}]$, and study their thermal properties. It turns out that
whereas $\Gamma_{b}$ and $\Gamma_{+}$ decrease with increasing $T$ or $\mu$,
$\Gamma_{-}$ increases with increasing $T$ or $\mu$. This behavior
qualitatively changes by adding thermal corrections to $m_{b}^{0}$ and
$m_{f}^{0}$, while the difference between $\Gamma_{+}$ and $\Gamma_{-}$ keeps
increasing with increasing $T$ or $\mu$. Moreover, $\eta_{b}$ ($\eta_{f}$)
increases (decreases) with increasing $T$ or $\mu$. We show that the effect of
plasminos on $\eta_{f}$ becomes negligible with increasing (decreasing) $T$
($\mu$).
