Lotta interesting stuff out there today, none of which I understand the import of. Callups could be medical, I suppose. But the china virus ain’t that bad, so....?
He authorized the whole of the drilling Reserve across the board. While it includes the medical people, if required in the Marines it is also a full division/air wing/Force Service Support contingent. Last time it happened was Desert Storm. SecDef can pull the trigger to activate the drilling Reserves of the Army/Navy/Air Force for up to 24 months. In the Corps, that means 96 hours to mobilize once the order is received. With the airlines as they are, for the Wing components this should happen even faster.