  The Higgs mediated flavor violating bottom-strange quarks transitions induced
at the one-loop level by a nondiagonal $Hbs$ coupling are studied within the
context of an effective Yukawa sector that comprises $SU_L(2)\times
U_Y(1)$-invariant operators of up to dimension-six. The most recent
experimental result on $B\to X_s\gamma$ with hard photons is employed to
constraint the $Hbs$ vertex, which is used to estimate the branching ratio for
the $B_s\to \gamma\gamma$ decay. It is found that the $B_s\to \gamma\gamma$
decay can reach a branching ratio of the order of $4\times 10^{-8}$, which is 2
orders of magnitude more stringent than the current experimental limit.
