A 52-year-old woman with a 15-year history of alcohol dependence is admitted to a de-addiction centre for supervised withdrawal. On day 3 of abstinence, she develops visual hallucinations (seeing insects crawling on her skin), is oriented to person only, and has a temperature of 38.5°C. Vital signs: BP 160/100 mmHg, HR 120 bpm, respiratory rate 24/min. She is restless and diaphoretic. What is the most likely diagnosis, and what is the immediate next step?