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A 33yo woman comes to your clinic with bilateral cervical lymph node swelling and fatigue.

Examination: Afebrile. Several bilateral 1-2cm cervial lymph nodes that were soft, non-tender and freely movable. No other lymphadenopathy. Her chest was clear, heart sounds normal, but she had mild tenderness at the right costal margin on deep inspiration.

Lab studies: Hct 37% WBC 5,200/uL, ALT 75 units, AST 70 units, AlkPhos 140 units. UA nml.

What is the (infectious) differential? What testing do you want?