Is the supplication recited upon seeing someone afflicted specific to Muslims only, or does it include non-believers as well?

It is prescribed to say the supplication, "Praise be to Allah, who has spared me from what He has afflicted you with, and preferred me over many of those whom He has created with a great preference," upon seeing an afflicted disbeliever. This is because the benefit accrues to the supplicant, and it encompasses both religious and worldly afflictions, such as physical ailments, immorality, injustice, and disbelief.