On 11 May 2016, nine Sherpas summited Mount Everest. The next day another six persons reached the top. These were the first summitings since 2014, when 106 made it to the top. By 13 May, 42 climbers had reached the summit and by 22 May, good weather had allowed over 400 climbers to reach the summit. However, about 30 climbers developed frostbite or became sick, and two climbers died from what was reported as possible altitude sickness. Among those that had to turn back was a science expedition attempting to study the link between hypoxia and cognitive decline. Although it did not run its course, it did give some clues into the effects of high-altitude acclimatisation on human blood.