pertussis

A 3-month-old male presents with persistent fever, decreased oral intake, and worsening cough associated with post-tussive emesis for the five days. Parents state that the patient’s older sibling has had similar symptoms for the past two weeks and that neither child has received vaccinations after birth. The patient presents with BP 98/64 mm Hg, HR 160, RR 62, T 38.1ºC. Physical exam demonstrates an ill-appearing infant with bilateral conjunctival hemorrhage, dry cough, and inspiratory “whooping” sound. What is the most likely cause of this patient’s symptoms and what are the next steps in management?