The ESV blog points out that the ESV:
translates Luke 1:34 as, “How will this be, since I am a virgin?” and adds the footnote “Greek since I do not know a man.”The ESV wording here is better than a literal translation. It accurately translates the figurative meaning of the Greek of Luke 1:34 for English speakers. A literal translation of "I do not know a man" does not communicate that figurative meaning so accurately to many, perhaps most, English speakers today. In fact, it is literally not true, since Mary likely knew several men, including her own father and her betrothed, Joseph.