Muscaphobia

Muscaphobia (from Latin musca, "fly") is the fear of. Though they're harmless, flies are bothersome to many people when in the house. Sufferers of muscaphobia would either stay in the enclosed room or not let anybody open up outside door even briefly, meaning everyone living in the sufferer's residence would be stuck in the house. If a muscaphobe sees a fly, a person would scream, flee and yell anyone to kill that fly. Though some may spend hours obsessing over the fly/flies and try to kill them without touching them.