Beechcraft / Beech Aircraft Corp Undifferentiated or Other Model
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 28
Human-Machine Interface
Conflict NMAC
Flight Crew Requested ATC Assistance / Clarification
Aircraft
I accepted a hand off on Aircraft X from GSO approach. He was flying from INT to IPT; VFR/035. Sector traffic was light at this time. When I handed him off to ROA approach; sector complexity had increased. I had an aircraft on approach into DAN. A previously issued restriction to an aircraft landing GSO had to be amended when I received traffic for him from ZTL. In addition multiple departures when coming out of the Washington Metro Area. When I attempted to transfer communications to ROA; multiple aircraft were calling and I don't believe he heard the change request clearly. Shortly afterward he asked me if I had seen VFR traffic for him and that he almost had a mid-air collision. When he said that; I had seen the target that was now behind him. He then asked for the correct ROA frequency.I was working on a big sector range to cover my airspace. This does minimize my view of the areas where VFR targets are more prominent. Working on a smaller range may be possible. There was a short burst of IFR transitional traffic that took my attention away from VFR traffic. A CPC D-side may have helped in this situation. Possibly knowing of a short burst in traffic volume may have helped.
ZDC Controller reported an NMAC between an aircraft under ZDC's control and an unseen VFR aircraft.