The mythic power Infectious Spell has this qualification
Whenever you cast a spell that specifically targets a limited number of targets (such as “one creature/level” or “one or more creatures”) and has a duration longer than 1 round, you can expend one use of mythic power to make the spell infectious.
Do spells that specifically target only "one creature" count as a "limited number of targets"?
For examples, consider Hold Person ("One humanoid creature") — would it be a valid spell for Infectious Spell?