For all of us who spend countless hours researching every possible thing that can go wrong on the mountain and preparing for it all, most do not even think about the possibility of HAPE as it is considerably rare.
A year ago, I wrote about HAPE on Mt. Whitney, but the focus was different:
Dexamethasone and HAPE The entire link is worth reading, but I'll extract a little of it here: Estimates for the likelihood of contracting HAPE seem to vary all over the map, according to the many different studies. Assuming 160 people a day climb Mt. Whitney, the estimates translate from a low of one person every two months to a high of seven per day. (One study suggests up to 24 per day.)
Why don't we observe more of it? Again, from the link: "I have long suspected that unrecognized cases of HAPE (incipient, perhaps) among Mt. Whitney visitors are more frequent than commonly thought. For any number of reasons the afflicted person may turn around and descend, thereby quickly and easily correcting the situation--without ever having been aware of what it was."
As far as AMS is concerned, it appears that 1/3 to 1/2 of unacclimatized Mt. Whitney hikers experience it. The key word is "unacclimatized." Many who try Whitney are acclimatized, either because they've prepared well with the hints mentioned on this forum, or simply because they go to and stay at altitude frequently.
