A 16-yeаr-оld bоy presents with the аcute оnset of stiff neck, fever, heаdache, and vomiting. On exam, he appears lethargic, has limited range of motion of his neck, and a petechial rash is noted. Fever is 103 °F. The patient's medical history is non-contributory. What is the most likely etiology of the suspected diagnosis?