Differential Diagnosis

The patient's symptoms and physical examination findings suggest a respiratory infection. Here's a breakdown of the differential diagnosis:

• Single most likely diagnosis
  • Community-acquired pneumonia (CAP): The patient's symptoms, such as sore throat, fatigue, headache, chills, cough, and shortness of breath, along with the physical examination findings of slightly diminished breath sounds in the right posterior chest region and patchy consolidation in the right lower lobe on chest radiograph, are consistent with CAP. The fact that many of her sorority sisters have similar symptoms suggests a contagious cause, which is also consistent with CAP.
• Other Likely diagnoses
  • Influenza: The patient's symptoms, such as sore throat, fatigue, headache, chills, and cough, are consistent with influenza, especially given the fact that many of her sorority sisters have similar symptoms.
  • Acute bronchitis: The patient's symptoms, such as cough and shortness of breath, could be consistent with acute bronchitis, although the presence of patchy consolidation on chest radiograph makes CAP more likely.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Pneumococcal pneumonia with sepsis: Although the patient's vital signs do not suggest sepsis at this time, pneumococcal pneumonia can progress rapidly to sepsis, which would be life-threatening.
  • Influenza pneumonia with secondary bacterial infection: Influenza can increase the risk of secondary bacterial infections, such as Staphylococcus aureus or Streptococcus pneumoniae, which can be life-threatening.
  • Mycoplasma pneumonia with hemolytic anemia: Mycoplasma pneumonia can cause hemolytic anemia, which can be life-threatening if not recognized and treated promptly.
• Rare diagnoses
  • Tuberculosis (TB): Although TB is less likely given the patient's age and lack of exposure history, it should be considered in the differential diagnosis, especially if the patient has a history of travel to or contact with someone from a TB-endemic area.
  • Pneumonia caused by atypical organisms (e.g., Legionella, Chlamydia): These organisms can cause pneumonia, but are less common and typically require specific risk factors or exposures.

In terms of treatment, oral azithromycin would be an appropriate choice for CAP, especially given the patient's age and lack of comorbidities. However, the final treatment decision should be based on the patient's specific clinical presentation, laboratory results, and local antibiotic resistance patterns.