Answer: The etiology of the symptoms is the bacterium Bordetella pertussis.
Explanation: Etiology implies the "cause of" or "origin of" a disease. Paroxysmal cough is most commonly caused by the bacterium Bordetella pertussis. The cough is also accompanied by mucus accumulation in the airways. The bacterium infects the respiratory tract of an individual causing consistent coughing and excessive mucus production.