Emergency services were called to the serious collision at Washington roundabout at around 7.30am.
Members of the Air Ambulance team also attended and the helicopter landed just north of the roundabout at 8.30am.
A man was cut out of the van by firefighters and was airlifted to hospital.
Paramedics also treated three other people at the scene.
A police spokesman added several passengers were aboard the bus. One suffered minor injuries.
The northbound carriageways were closed following the crash. Both are now re-open.
Related stories: PHOTOS: A24 chaos after air ambulance called to bus and van crash
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