Review the pharyngitis scenarios and determine the most likely cause, including pathogen and mode of transmission. Discuss data that support your decision and treatment strategies.
Scenario 1: Susan is a 16-year-old with sudden onset of severe sore throat for the past day. She feels like she had a fever but did not check her temperature (i.e., subjective fever). She states it is very painful to swallow, and she thinks she sees white spots on her throat. She denies cough, rhinorrhea, nausea, otalgia, shortness of breath, or headache. She reports no exposure to sick individuals.

Medications: None
Allergies: None
Social History: Nonsmoker and drinks alcohol (two to three beers) one to two times a month
Physical Examination:

Vital Signs: Temperature 101.0°F; Pulse 100 beats per minute; Respirations 18 per minute; Blood Pressure 110/66 mmHg
General: Ill and tired appearance
Head, Eyes, Ears, Nose, and Throat: Unremarkable except for erythematous oropharynx with small petechiae and white tonsillar exudates
Neck: Anterior cervical lymphadenopathy; two on right, three on left; all small (<0.5 cm) and tender
Cardiovascular, Lungs, and Abdomen: Unremarkable

What is the most likely diagnosis and pathogen causing this disorder and mode of transmission?