  We address the evolution of heavy-quarkonium states in an expanding
quark-gluon plasma by implementing effective field theory techniques in the
framework of open quantum systems. In this setting we compute the nuclear
modification factors for quarkonia that are $S$-wave Coulombic bound states in
a strongly-coupled quark-gluon plasma. The calculation is performed at an
accuracy that is leading-order in the heavy-quark density expansion and
next-to-leading order in the multipole expansion. The quarkonium density-matrix
evolution equations can be written in the Lindblad form, and, hence, they
account for both dissociation and recombination. Thermal mass shifts, thermal
widths and the Lindblad equation itself depend on only two non-perturbative
parameters: the heavy-quark momentum diffusion coefficient and its dispersive
counterpart. Finally, by numerically solving the Lindblad equation, we provide
results for the $\Upsilon(1S)$ and $\Upsilon(2S)$ suppression.
