A three year old child is brought in by parents with abrupt onset fever (39.5C), sore throat, dysphagia, and drooling. This has only been going on for the last 12 hours, but the child looks toxic. WBC is elevated at 25,000/mm3 with increased neutrophils and bands. The child complains that he can't breathe and feels like choking when he inspires. He is anxious, restless, irritable, and his speech is muffled but not hoarse. The child is sitting with his arms back, trunk leaning forward, neck hyperextended, and chin thrust forward. No stridor is heard. The child has not received any vaccinations.
Challenge: What is the causative agent?
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