A 38-year-old homeless man is brought to the emergency department due to severe muscle pain and stiffness. He arrived at a homeless shelter 2 days ago, and the manager says that he has been restless and irritable. The patient has a history of alcohol abuse and injection drug use. Temperature is 37.7 C (100 F), blood pressure is 150/90 mm Hg, and pulse is 102/min. Both pupils are normal, equal, and reactive to light There are marks on the patient's arms from previous injections as well as several abrasions and lacerations on the lower extremities. He is unable to open his mouth completely. Painful spasms of the neck muscles are triggered by physical stimuli.