High incidence of mild acute mountain sickness in conference attendees at 10 000 foot altitude

An epidemic of mild acute mountain sickness (AMS) occurred at a 4-day meeting of epidemiologists held at an altitude of 3000 m (9800 ft) in the Rocky Mountains of Colorado, USA. Questionnaires from 96% of the 105 attendees documented the following symptom frequencies: headache, 59%; shortness of breath, 59%; difficulty in sleeping, 45%; weakness or dizziness, 40%; and nausea, 12%. AMS, defined as three or more symptoms, occurred in 42% of the respondents, and 90% had at least one symptom. One third felt the illness interfered with their concentration at the meeting, and 31% would not plan another meeting at this altitude, although only one person missed meeting sessions as a result of the AMS. AMS should be anticipated by those planning meetings of short duration at high altitude, and by physicians advising travelers to altitudes over 2000 m.