Black mold spreading around ceiling AC vents

We noticed small dark specks around our bedroom AC supply vent a month ago, but now it has spread into a 30cm dark ring across the ceiling drywall. The room smells musty whenever the air conditioner runs. Is this black mold toxic to breathe, and can I scrub it off with bleach solution, or does the entire drywall section need replacing along with duct cleaning in Sharjah? We have a newborn in the house so I want to handle this safely.