Hi and thank you for choosing HCM to post your question. Whooping and barking sound during cough are due to laryngotracheal pertussis infection. What is his vaccination status? Did he has other symptoms ,for example nasal congestion,tearing ect? Pertussis infection is a disease carachterized by three stages :catarrhal with nasal congestion,rhinorrhea,sneezing;paroxysmal phase carachterized by paroxysm of intense coughing and a convalescent stage carachterized by chronic cough. The mainstay of treatment is supportive therapy with good nutrition and plenty of rest.Antibiotics initiated during the paroxysmal stage( in which it looks to be your son) do not affect the duration and severity of illness but can prevent or alleviate secondary bacterial infection.Azithromycin is a good choice. I hope my opinion can be helpful . Kind regards Dr.Dushi