Chasidim of the Satmar Rebbe, R' Aaron Teitelbaum, had a scare on the first day of Rosh HaShana, when their Rebbe suddenly took ill.
Tuesday morning, the first day of Rosh HaShana, the Rebbe arrived at his Williamsburg Beis Medrash at around 8:00 a.m. and began Davening. After about an hour the Rebbe began to sweat profusely, and was taken by a fit of chills, causing him to tremble uncontrollably.
Hatzolah quickly ruled out any heart-related issues; rather, it was determined that the Rebbe was suffering from exhaustion and dehydration. The Rebbe indicated that the previous two nights, the night of Slichos of Erev Rosh HaShana, as well as the night of Rosh HaShana, he had risen well before daybreak and had hardly slept. In addition, he had drank nothing that morning, not wishing to consume any liquids until after hearing the blowing of the Shofar.