A 60-year-old male presents with fever, dry cough, headache, nausea, vomiting and diarrhea. He saw his primary care physician who prescribed him Amoxicillin for which he has been taking for 4 days but feeling worse. Labs show a Sodium of 130 and mild transaminitis, other labs are within normal limits. What is the most likely diagnosis?

A. Tularemia

B. Hantavirus

C. Legionella

D. Q-fever

E. PCP pneumonia

Answer: C - Legionella

-Micro: Gram negative bacillus found in water systems.

-Clinical: pneumonia type symptoms + GI symptoms +/- neuro symptoms (confusion, ataxia); can have associated fever-pulse dissociation (relative bradycardia in setting of fever).

-Hyponatremia and transaminitis are common lab findings in Legionella.

-Diagnosis is via urinary antigen test.