A five-year-old boy is brought to his pediatrician by his mother. She says that her son has had a persistent cough for 2 weeks. She describes the coughing as "occasional fits of coughing where he can’t even breathe," often followed by an inspiratory ‘whoop’ sound. Sometimes he vomits after the coughing episodes. The boy attends daycare, and the mom is concerned he picked something up from the other children. The boy has not had many of his vaccines, as his mom is worried that he would get autism. What is the likely cause of his cough