From the OP "becoming airborne a call went out over the PA asking for a medical professional"
Who was the medical professional? It could have been (presuming one was on the flight not stated in theOP) a nurse, dentist or a doctor. From reading the past posts, all (in my reading) come to the conclusion that this was a cardiac arrest.
What if the death was caused by some contagious disease, take your pick. I would hope airlines would carry body bags for this scenario. I would be very concerned sitting in the vicinity of a person who has died from TB for twelve hours in a sealed tube.