A 32-year-old woman presents to the emergency department after acutely developing a high fever, lightheadedness on standing, and a rash. At the hospital she develops vomiting, diarrhea, confusion, and abdominal pain. She goes on to develop evidence of multiorgan failure and is transferred to the intensive care unit. One week after the acute illness she develops desquamation of the skin. On further history, the illness started 3 days after the onset of menstruation. Which of the following is the most likely diagnosis?