  We study the spectroscopy and transport properties of charmed mesons in a
thermal medium by applying an effective field theory based on chiral and
heavy-quark symmetries in the imaginary time formalism. Relying on unitarity
constraints and self-consistency we extract the in-medium properties (masses
and widths) of $D$ and $D_s$ mesons and their interactions with light hadrons.
We report our findings on 1) dynamically generated states, 2) thermal evolution
of chiral partners, 3) in-medium scattering amplitudes, and 4) transport
coefficients below the chiral restoration temperature.
