Climbing high mountains is risky and the speed at which trekkers ascend Mount Kilimanjaro increases their chances of getting altitude sickness.

Dr Charlotte Noble, a climber who has been an expedition doctor on three high-altitude trips, said: "Kilimanjaro is especially risky because people think it is easy. But it is too high to do in such a short time. They don't trek for long enough to acclimatise properly."The higher a mountain, the thinner the oxygen in the air, and this can cause altitude sickness. Symptoms include headaches, nausea and difficulty breathing. In severe cases, climbers risk death if they do not descend.Trekkers on typical four- to five-day Kilimanjaro trips had a 60% chance of reaching the summit and a 77% chance of developing altitude sickness if they did the ascent in less than five days, said expedition doctor Ross Hofmeyr, citing a 2009 study published in the Wilderness and Environmental Medicine Journal.story_article_left1To avoid altitude sickness they should climb in slow stages to allow their bodies to adapt, but most trips to Kilimanjaro don't allow time for this.Climbing groups on Kilimanjaro tend to gain altitude relatively quickly because they want to do the trip in less than a week for financial and logistical reasons. In contrast, trekkers to the Everest base camp follow international guidelines and ascend no more than 500m each day once they are above 3,000m.Sean Disney, a guide who has been to the 5,895m summit of Kilimanjaro 21 times, said: "Six to seven days on Kilimanjaro is fine because the climbers acclimatise to about 4,700m and punch in and out of the summit zone quickly."People take a calculated risk, like any endurance sport, when climbing high mountains. A health-related issue compounded by altitude becomes a deadly formula," he said.Gugu Zulu had flu-like symptoms on Kilimanjaro that were being monitored, but he felt well enough to keep going.He was an extreme athlete who had completed endurance events such as the 89km Comrades Marathon and 650km Cape Epic mountain bike race. But fitness is no protection against the effects of altitude.Disney said: "If people have breathing problems the only solution is descent. They can recover from altitude sickness in two hours if they drop down 500m, and 95% of the time they recover."Thousands of people climbed the mountain every year and most came down safely, said Hofmeyr, but "if you spend less than seven days on Kilimanjaro you are putting yourself at an unnecessary, irresponsible risk".The death toll on Kilimanjaro is unconfirmed, but reports estimate it at 10 or more a year...