Its not just Apple
HP's prohibiting anyone who isn't already there from traveling to China at all without a full risk assessment and approval from EH&S being done first. Unless you're Carl Icahnt or Xerox's board of puppets directors, then we'd just love it if you visit, and you don't have to come back, hell we'll pay for the trip.
Seriously now, I'd imagine other big hardware companies are likely doing the same, we've all got to do business with China but its lunacy to not take some sort of precautions, especially considering Wuhan is basically their equivalent to Atlanta or Schiphol with the amount of people transiting it at any given time.