What sort of problem is altitude illness?

Altitude illness: Altitude illness can be a serious problem. If not recognized early , it can be fatal. The key aspect of prevention is to acclimatize yourself to a medium altitude before you go to high altitude. Consultation with an md can get you medicine to reduce the risk of illness. Many people (eg, skiers at 5000') experience mild illness--jittery, headache, insomnia. These mean it is time to take a break.

A poor term / Broad: 1. Acute mountain sickness w/ headache, nausea, irritability 2 as climb > 8000 meters, risk for high altitude pulmonary edema (hape). Fluid in lungs, short of breath, can be fatal 3. Also, at same altitude: high altitude cerebral edema(hace)confusion, staggering, sleepiness. Also can be fatal if concerned you are going to signif altitude, see a wilderness medicine or travel provider.